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"
 ]