fix: security hardening + performance refactoring (code review batch 1)

- IDOR fix: deliberation vote now verifies juryMemberId === ctx.user.id
- Rate limiting: tRPC middleware (100/min), AI endpoints (5/hr), auth IP-based (10/15min)
- 6 compound indexes added to Prisma schema
- N+1 eliminated in processRoundClose (batch updateMany/createMany)
- N+1 eliminated in batchCheckRequirementsAndTransition (3 batch queries)
- Service extraction: juror-reassignment.ts (578 lines)
- Dead code removed: award.ts, cohort.ts, decision.ts (680 lines)
- 35 bare catch blocks replaced across 16 files
- Fire-and-forget async calls fixed
- Notification false positive bug fixed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/server/services/notification.ts

@@ -104,8 +104,8 @@ export async function sendNotification(
 
   // Overall success if at least one channel succeeded
   result.success =
-    (result.channels.email?.success ?? true) ||
-    (result.channels.whatsapp?.success ?? true)
+    (result.channels.email?.success ?? false) ||
+    (result.channels.whatsapp?.success ?? false)
 
   return result
 }