step 3.2 complete: agent CRUD API routes

- Add app/api/routes/agents.py with 11 endpoints:
  GET/POST/PUT/DELETE /agents/local (local directory agent configs)
  GET/POST/PUT/DELETE /agents/cloud (cloud connector agent configs)
  GET /agents/catalog (hardcoded agent type catalog)
  GET /agents/runs (paginated run logs with agent_id/page/limit filters)
  POST /agents/{id}/run (manual trigger stub, dispatch wired in step 3.4)
- Tier-gate creation via combined local+cloud batch_active limit
- Ownership checks on all mutations (404 on mismatch)
- Cascade delete of run logs via SQLAlchemy relationship
- Register agents router in app/main.py
- Fix missing import json in app/agents/task_agent.py

app/main.py

@@ -43,7 +43,7 @@ def create_app() -> FastAPI:
     app.add_middleware(SanitizerMiddleware)
     app.add_middleware(TierRateLimitMiddleware)
 
-    from app.api.routes import auth, backup, billing, chat, plans, plugins, storage, vectors
+    from app.api.routes import agents, auth, backup, billing, chat, plans, plugins, storage, vectors
 
     app.include_router(auth.router,     prefix="/api/v1")
     app.include_router(chat.router,     prefix="/api/v1")
@@ -53,6 +53,7 @@ def create_app() -> FastAPI:
     app.include_router(backup.router,   prefix="/api/v1")
     app.include_router(plugins.router,  prefix="/api/v1")
     app.include_router(billing.router,  prefix="/api/v1")
+    app.include_router(agents.router,   prefix="/api/v1")
 
     @app.get("/api/v1/health", tags=["health"])
     async def health() -> dict: