Add organization management and admin-specific APIs

- Introduced schemas for organizations, including creation, updates, and responses.
- Created models for `Organization` and `UserOrganization` with role-based access control and relationships.
- Implemented admin APIs for managing users, organizations, and bulk actions.
- Added advanced filtering, sorting, and pagination for user and organization queries.
- Updated `CRUD` logic to support organization-specific operations and member management.
- Enhanced database with necessary indexes and validation for improved performance and data integrity.

backend/app/api/main.py

@@ -1,8 +1,10 @@
 from fastapi import APIRouter
 
-from app.api.routes import auth, users, sessions
+from app.api.routes import auth, users, sessions, admin, organizations
 
 api_router = APIRouter()
 api_router.include_router(auth.router, prefix="/auth", tags=["Authentication"])
 api_router.include_router(users.router, prefix="/users", tags=["Users"])
 api_router.include_router(sessions.router, prefix="/sessions", tags=["Sessions"])
+api_router.include_router(admin.router, prefix="/admin", tags=["Admin"])
+api_router.include_router(organizations.router, prefix="/organizations", tags=["Organizations"])