feat: implement custom fields, gantt view, calendar view, and file encryption

- Custom Fields (FEAT-001):
  - CustomField and TaskCustomValue models with formula support
  - CRUD API for custom field management
  - Formula engine for calculated fields
  - Frontend: CustomFieldEditor, CustomFieldInput, ProjectSettings page
  - Task list API now includes custom_values
  - KanbanBoard displays custom field values

- Gantt View (FEAT-003):
  - TaskDependency model with FS/SS/FF/SF dependency types
  - Dependency CRUD API with cycle detection
  - start_date field added to tasks
  - GanttChart component with Frappe Gantt integration
  - Dependency type selector in UI

- Calendar View (FEAT-004):
  - CalendarView component with FullCalendar integration
  - Date range filtering API for tasks
  - Drag-and-drop date updates
  - View mode switching in Tasks page

- File Encryption (FEAT-010):
  - AES-256-GCM encryption service
  - EncryptionKey model with key rotation support
  - Admin API for key management
  - Encrypted upload/download for confidential projects

- Migrations: 011 (custom fields), 012 (encryption keys), 013 (task dependencies)
- Updated issues.md with completion status

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/models/__init__.py

@@ -12,6 +12,7 @@ from app.models.notification import Notification
 from app.models.blocker import Blocker
 from app.models.audit_log import AuditLog, AuditAction, SensitivityLevel, EVENT_SENSITIVITY, ALERT_EVENTS
 from app.models.audit_alert import AuditAlert
+from app.models.encryption_key import EncryptionKey
 from app.models.attachment import Attachment
 from app.models.attachment_version import AttachmentVersion
 from app.models.trigger import Trigger, TriggerType
@@ -19,13 +20,18 @@ from app.models.trigger_log import TriggerLog, TriggerLogStatus
 from app.models.scheduled_report import ScheduledReport, ReportType
 from app.models.report_history import ReportHistory, ReportHistoryStatus
 from app.models.project_health import ProjectHealth, RiskLevel, ScheduleStatus, ResourceStatus
+from app.models.custom_field import CustomField, FieldType
+from app.models.task_custom_value import TaskCustomValue
+from app.models.task_dependency import TaskDependency, DependencyType
 
 __all__ = [
     "User", "Role", "Department", "Space", "Project", "TaskStatus", "Task", "WorkloadSnapshot",
     "Comment", "Mention", "Notification", "Blocker",
     "AuditLog", "AuditAlert", "AuditAction", "SensitivityLevel", "EVENT_SENSITIVITY", "ALERT_EVENTS",
-    "Attachment", "AttachmentVersion",
+    "EncryptionKey", "Attachment", "AttachmentVersion",
     "Trigger", "TriggerType", "TriggerLog", "TriggerLogStatus",
     "ScheduledReport", "ReportType", "ReportHistory", "ReportHistoryStatus",
-    "ProjectHealth", "RiskLevel", "ScheduleStatus", "ResourceStatus"
+    "ProjectHealth", "RiskLevel", "ScheduleStatus", "ResourceStatus",
+    "CustomField", "FieldType", "TaskCustomValue",
+    "TaskDependency", "DependencyType"
 ]

backend/app/models/attachment.py

@@ -16,6 +16,11 @@ class Attachment(Base):
     file_size = Column(BigInteger, nullable=False)
     current_version = Column(Integer, default=1, nullable=False)
     is_encrypted = Column(Boolean, default=False, nullable=False)
+    encryption_key_id = Column(
+        String(36),
+        ForeignKey("pjctrl_encryption_keys.id", ondelete="SET NULL"),
+        nullable=True
+    )
     uploaded_by = Column(String(36), ForeignKey("pjctrl_users.id", ondelete="SET NULL"), nullable=True)
     is_deleted = Column(Boolean, default=False, nullable=False)
     created_at = Column(DateTime, server_default=func.now(), nullable=False)
@@ -24,6 +29,7 @@ class Attachment(Base):
     # Relationships
     task = relationship("Task", back_populates="attachments")
     uploader = relationship("User", foreign_keys=[uploaded_by])
+    encryption_key = relationship("EncryptionKey", foreign_keys=[encryption_key_id])
     versions = relationship("AttachmentVersion", back_populates="attachment", cascade="all, delete-orphan")
 
     __table_args__ = (

backend/app/models/custom_field.py

@@ -0,0 +1,37 @@
+import uuid
+import enum
+from sqlalchemy import Column, String, Text, Boolean, DateTime, ForeignKey, Enum, JSON, Integer
+from sqlalchemy.sql import func
+from sqlalchemy.orm import relationship
+from app.core.database import Base
+
+
+class FieldType(str, enum.Enum):
+    TEXT = "text"
+    NUMBER = "number"
+    DROPDOWN = "dropdown"
+    DATE = "date"
+    PERSON = "person"
+    FORMULA = "formula"
+
+
+class CustomField(Base):
+    __tablename__ = "pjctrl_custom_fields"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    project_id = Column(String(36), ForeignKey("pjctrl_projects.id", ondelete="CASCADE"), nullable=False)
+    name = Column(String(100), nullable=False)
+    field_type = Column(
+        Enum("text", "number", "dropdown", "date", "person", "formula", name="field_type_enum"),
+        nullable=False
+    )
+    options = Column(JSON, nullable=True)  # For dropdown: list of options
+    formula = Column(Text, nullable=True)  # For formula: formula expression
+    is_required = Column(Boolean, default=False, nullable=False)
+    position = Column(Integer, default=0, nullable=False)  # For ordering fields
+    created_at = Column(DateTime, server_default=func.now(), nullable=False)
+    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now(), nullable=False)
+
+    # Relationships
+    project = relationship("Project", back_populates="custom_fields")
+    values = relationship("TaskCustomValue", back_populates="field", cascade="all, delete-orphan")

backend/app/models/encryption_key.py

@@ -0,0 +1,22 @@
+"""EncryptionKey model for AES-256 file encryption key management."""
+import uuid
+from sqlalchemy import Column, String, Text, Boolean, DateTime
+from sqlalchemy.sql import func
+from app.core.database import Base
+
+
+class EncryptionKey(Base):
+    """
+    Encryption key storage for file encryption.
+
+    Keys are encrypted with the Master Key before storage.
+    Only system admin can manage encryption keys.
+    """
+    __tablename__ = "pjctrl_encryption_keys"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    key_data = Column(Text, nullable=False)  # Encrypted key using Master Key
+    algorithm = Column(String(20), default="AES-256-GCM", nullable=False)
+    is_active = Column(Boolean, default=True, nullable=False)
+    created_at = Column(DateTime, server_default=func.now(), nullable=False)
+    rotated_at = Column(DateTime, nullable=True)  # When this key was superseded

backend/app/models/project.py

@@ -40,3 +40,4 @@ class Project(Base):
     tasks = relationship("Task", back_populates="project", cascade="all, delete-orphan")
     triggers = relationship("Trigger", back_populates="project", cascade="all, delete-orphan")
     health = relationship("ProjectHealth", back_populates="project", uselist=False, cascade="all, delete-orphan")
+    custom_fields = relationship("CustomField", back_populates="project", cascade="all, delete-orphan")

backend/app/models/task.py

@@ -30,6 +30,7 @@ class Task(Base):
     original_estimate = Column(Numeric(8, 2), nullable=True)
     time_spent = Column(Numeric(8, 2), default=0, nullable=False)
     blocker_flag = Column(Boolean, default=False, nullable=False)
+    start_date = Column(DateTime, nullable=True)
     due_date = Column(DateTime, nullable=True)
     position = Column(Integer, default=0, nullable=False)
     created_by = Column(String(36), ForeignKey("pjctrl_users.id"), nullable=False)
@@ -55,3 +56,18 @@ class Task(Base):
     blockers = relationship("Blocker", back_populates="task", cascade="all, delete-orphan")
     attachments = relationship("Attachment", back_populates="task", cascade="all, delete-orphan")
     trigger_logs = relationship("TriggerLog", back_populates="task")
+    custom_values = relationship("TaskCustomValue", back_populates="task", cascade="all, delete-orphan")
+
+    # Dependency relationships (for Gantt view)
+    predecessors = relationship(
+        "TaskDependency",
+        foreign_keys="TaskDependency.successor_id",
+        back_populates="successor",
+        cascade="all, delete-orphan"
+    )
+    successors = relationship(
+        "TaskDependency",
+        foreign_keys="TaskDependency.predecessor_id",
+        back_populates="predecessor",
+        cascade="all, delete-orphan"
+    )

backend/app/models/task_custom_value.py

@@ -0,0 +1,24 @@
+import uuid
+from sqlalchemy import Column, String, Text, DateTime, ForeignKey, UniqueConstraint
+from sqlalchemy.sql import func
+from sqlalchemy.orm import relationship
+from app.core.database import Base
+
+
+class TaskCustomValue(Base):
+    __tablename__ = "pjctrl_task_custom_values"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    task_id = Column(String(36), ForeignKey("pjctrl_tasks.id", ondelete="CASCADE"), nullable=False)
+    field_id = Column(String(36), ForeignKey("pjctrl_custom_fields.id", ondelete="CASCADE"), nullable=False)
+    value = Column(Text, nullable=True)  # Stored as text, parsed based on field_type
+    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now(), nullable=False)
+
+    # Unique constraint: one value per task-field combination
+    __table_args__ = (
+        UniqueConstraint('task_id', 'field_id', name='uq_task_field'),
+    )
+
+    # Relationships
+    task = relationship("Task", back_populates="custom_values")
+    field = relationship("CustomField", back_populates="values")

backend/app/models/task_dependency.py

@@ -0,0 +1,68 @@
+from sqlalchemy import Column, String, Integer, Enum, DateTime, ForeignKey, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+from app.core.database import Base
+import enum
+
+
+class DependencyType(str, enum.Enum):
+    """
+    Task dependency types for Gantt chart.
+
+    FS (Finish-to-Start): Predecessor must finish before successor starts (most common)
+    SS (Start-to-Start): Predecessor must start before successor starts
+    FF (Finish-to-Finish): Predecessor must finish before successor finishes
+    SF (Start-to-Finish): Predecessor must start before successor finishes (rare)
+    """
+    FS = "FS"  # Finish-to-Start
+    SS = "SS"  # Start-to-Start
+    FF = "FF"  # Finish-to-Finish
+    SF = "SF"  # Start-to-Finish
+
+
+class TaskDependency(Base):
+    """
+    Represents a dependency relationship between two tasks.
+
+    The predecessor task affects when the successor task can be scheduled,
+    based on the dependency_type. This is used for Gantt chart visualization
+    and date validation.
+    """
+    __tablename__ = "pjctrl_task_dependencies"
+
+    __table_args__ = (
+        UniqueConstraint('predecessor_id', 'successor_id', name='uq_predecessor_successor'),
+    )
+
+    id = Column(String(36), primary_key=True)
+    predecessor_id = Column(
+        String(36),
+        ForeignKey("pjctrl_tasks.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True
+    )
+    successor_id = Column(
+        String(36),
+        ForeignKey("pjctrl_tasks.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True
+    )
+    dependency_type = Column(
+        Enum("FS", "SS", "FF", "SF", name="dependency_type_enum"),
+        default="FS",
+        nullable=False
+    )
+    lag_days = Column(Integer, default=0, nullable=False)
+    created_at = Column(DateTime, server_default=func.now(), nullable=False)
+
+    # Relationships
+    predecessor = relationship(
+        "Task",
+        foreign_keys=[predecessor_id],
+        back_populates="successors"
+    )
+    successor = relationship(
+        "Task",
+        foreign_keys=[successor_id],
+        back_populates="predecessors"
+    )