feat: add case-level AI summary endpoint

POST /api/cases/:caseId/summarize combines extracted text from all of
a case's documents and runs the existing AI analysis prompt, storing
the result as a case-level analysis (document_id: null). Powers the
"Özet Hazırla" button on the case detail screen.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/routes/case.routes.ts

@@ -1,10 +1,11 @@
 import { Router } from 'express';
 import { requireAuth } from '../middleware/auth';
-import { createCase, deleteCase } from '../controllers/case.controller';
+import { createCase, deleteCase, summarizeCase } from '../controllers/case.controller';
 
 const router = Router();
 
 router.post('/', requireAuth, createCase);
 router.delete('/:caseId', requireAuth, deleteCase);
+router.post('/:caseId/summarize', requireAuth, summarizeCase);
 
 export default router;