Add schema reconciliation migration and file removal in bulk upload

Migration:
- Add standalone hasConflict index on ConflictOfInterest
- Ensure roundId is nullable on ConflictOfInterest
- Drop stale composite roundId_hasConflict index

Bulk upload:
- Add trash icon button to remove uploaded files
- Uses existing file.delete endpoint with audit logging

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

prisma/migrations/20260217000000_schema_reconciliation/migration.sql

@@ -0,0 +1,19 @@
+-- =============================================================================
+-- Schema Reconciliation: Fill remaining gaps between migrations and schema.prisma
+-- =============================================================================
+-- All statements are idempotent (safe to re-run on any database state).
+
+-- 1. ConflictOfInterest: add standalone hasConflict index (schema has @@index([hasConflict]))
+--    Migration 20260205223133 only created composite (roundId, hasConflict) index.
+CREATE INDEX IF NOT EXISTS "ConflictOfInterest_hasConflict_idx" ON "ConflictOfInterest"("hasConflict");
+
+-- 2. Ensure ConflictOfInterest.roundId is nullable (schema says String?)
+--    Pipeline migration (20260213) makes it nullable, but guard for safety.
+DO $$ BEGIN
+    ALTER TABLE "ConflictOfInterest" ALTER COLUMN "roundId" DROP NOT NULL;
+EXCEPTION WHEN others THEN NULL;
+END $$;
+
+-- 3. Drop stale composite index that no longer matches schema
+--    Schema only has @@index([hasConflict]) and @@index([userId]), not (roundId, hasConflict).
+DROP INDEX IF EXISTS "ConflictOfInterest_roundId_hasConflict_idx";