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

AI_REFACTOR_PLAN.md

@@ -322,7 +322,7 @@ Cloud Agent:
 - **Outcome:** Agent config and run tracking tables in PostgreSQL.
 
 ### Step 3.2 — Agent CRUD API routes
-- [ ] Create `app/api/routes/agents.py`:
+- [x] Create `app/api/routes/agents.py`:
   - `GET /api/v1/agents/catalog` — returns hardcoded agent type catalog:
     - `local_directory`: "Watches local directories, extracts data from files using AI"
     - `gmail`: "Scans Gmail inbox, extracts tasks/notes from emails"
@@ -343,7 +343,7 @@ Cloud Agent:
   - `GET /api/v1/agents/runs` — query params: `agent_id`, `page`, `limit` → paginated run logs
   - `POST /api/v1/agents/{id}/run` — manual trigger (dispatches to agent runner)
   - All routes require JWT auth; ownership enforced on all mutations
-- [ ] Register router in `app/main.py`
+- [x] Register router in `app/main.py`
 - **Files:** `app/api/routes/agents.py`, `app/main.py`
 - **Outcome:** Full CRUD for agent configs with tier-gated creation limits.