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/schemas/task.py

@@ -1,5 +1,5 @@
 from pydantic import BaseModel
-from typing import Optional, List
+from typing import Optional, List, Any, Dict
 from datetime import datetime
 from decimal import Decimal
 from enum import Enum
@@ -12,11 +12,27 @@ class Priority(str, Enum):
     URGENT = "urgent"
 
 
+class CustomValueInput(BaseModel):
+    """Input for setting a custom field value."""
+    field_id: str
+    value: Optional[Any] = None  # Can be string, number, date string, or user id
+
+
+class CustomValueResponse(BaseModel):
+    """Response for a custom field value."""
+    field_id: str
+    field_name: str
+    field_type: str
+    value: Optional[Any] = None
+    display_value: Optional[str] = None  # Formatted for display
+
+
 class TaskBase(BaseModel):
     title: str
     description: Optional[str] = None
     priority: Priority = Priority.MEDIUM
     original_estimate: Optional[Decimal] = None
+    start_date: Optional[datetime] = None
     due_date: Optional[datetime] = None
 
 
@@ -24,6 +40,7 @@ class TaskCreate(TaskBase):
     parent_task_id: Optional[str] = None
     assignee_id: Optional[str] = None
     status_id: Optional[str] = None
+    custom_values: Optional[List[CustomValueInput]] = None
 
 
 class TaskUpdate(BaseModel):
@@ -32,8 +49,10 @@ class TaskUpdate(BaseModel):
     priority: Optional[Priority] = None
     original_estimate: Optional[Decimal] = None
     time_spent: Optional[Decimal] = None
+    start_date: Optional[datetime] = None
     due_date: Optional[datetime] = None
     position: Optional[int] = None
+    custom_values: Optional[List[CustomValueInput]] = None
 
 
 class TaskStatusUpdate(BaseModel):
@@ -67,6 +86,7 @@ class TaskWithDetails(TaskResponse):
     status_color: Optional[str] = None
     creator_name: Optional[str] = None
     subtask_count: int = 0
+    custom_values: Optional[List[CustomValueResponse]] = None
 
 
 class TaskListResponse(BaseModel):