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/routers/file.ts

@@ -902,7 +902,9 @@ export const fileRouter = router({
           entityId: requirement.id,
           detailsJson: { name: input.name, roundId: input.roundId },
         })
-      } catch {}
+      } catch (err) {
+        console.error('[File] Audit log failed:', err)
+      }
 
       return requirement
     }),
@@ -938,7 +940,9 @@ export const fileRouter = router({
           entityId: id,
           detailsJson: data,
         })
-      } catch {}
+      } catch (err) {
+        console.error('[File] Audit log failed:', err)
+      }
 
       return requirement
     }),
@@ -961,7 +965,9 @@ export const fileRouter = router({
           entityType: 'FileRequirement',
           entityId: input.id,
         })
-      } catch {}
+      } catch (err) {
+        console.error('[File] Audit log failed:', err)
+      }
 
       return { success: true }
     }),
@@ -1594,7 +1600,8 @@ export const fileRouter = router({
           try {
             await client.statObject(bucket, objectKey)
             results[objectKey] = true
-          } catch {
+          } catch (err) {
+            console.error('Failed to stat MinIO object during existence check:', err)
             results[objectKey] = false
           }
         })