feat: implement task management module

Backend (FastAPI):
- Database migration for spaces, projects, task_statuses, tasks tables
- SQLAlchemy models with relationships
- Pydantic schemas for CRUD operations
- Spaces API: CRUD with soft delete
- Projects API: CRUD with auto-created default statuses
- Tasks API: CRUD, status change, assign, subtask support
- Permission middleware with Security Level filtering
- Subtask depth limit (max 2 levels)

Frontend (React + Vite):
- Layout component with navigation
- Spaces list page
- Projects list page
- Tasks list page with status management

Fixes:
- auth_client.py: use 'username' field for external API
- config.py: extend JWT expiry to 7 days
- auth/router.py: sync Redis session with JWT expiry

Tests: 36 passed (unit + integration)
E2E: All APIs verified with real authentication

OpenSpec: add-task-management archived

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

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

backend/app/schemas/__init__.py

@@ -2,6 +2,15 @@ from app.schemas.auth import LoginRequest, LoginResponse, TokenPayload
 from app.schemas.user import UserCreate, UserUpdate, UserResponse, UserInDB
 from app.schemas.department import DepartmentCreate, DepartmentUpdate, DepartmentResponse
 from app.schemas.role import RoleResponse
+from app.schemas.space import SpaceCreate, SpaceUpdate, SpaceResponse, SpaceWithOwner
+from app.schemas.project import (
+    ProjectCreate, ProjectUpdate, ProjectResponse, ProjectWithDetails, SecurityLevel
+)
+from app.schemas.task_status import TaskStatusCreate, TaskStatusUpdate, TaskStatusResponse
+from app.schemas.task import (
+    TaskCreate, TaskUpdate, TaskResponse, TaskWithDetails, TaskListResponse,
+    TaskStatusUpdate as TaskStatusChangeUpdate, TaskAssignUpdate, Priority
+)
 
 __all__ = [
     "LoginRequest",
@@ -15,4 +24,24 @@ __all__ = [
     "DepartmentUpdate",
     "DepartmentResponse",
     "RoleResponse",
+    "SpaceCreate",
+    "SpaceUpdate",
+    "SpaceResponse",
+    "SpaceWithOwner",
+    "ProjectCreate",
+    "ProjectUpdate",
+    "ProjectResponse",
+    "ProjectWithDetails",
+    "SecurityLevel",
+    "TaskStatusCreate",
+    "TaskStatusUpdate",
+    "TaskStatusResponse",
+    "TaskCreate",
+    "TaskUpdate",
+    "TaskResponse",
+    "TaskWithDetails",
+    "TaskListResponse",
+    "TaskStatusChangeUpdate",
+    "TaskAssignUpdate",
+    "Priority",
 ]