Consolidate @shieldai/db and @shieldsai/shared-db packages (FRE-4603)

- Merged singleton pattern + type exports from shared-db
- Kept FieldEncryptionService from original db package
- Upgraded to Prisma v6.2.0 (newer version)
- Adopted shared-db's complete schema for multi-service platform
- Updated 17 consumer imports across darkwatch, voiceprint, jobs, api
- Standardized on @shieldai/db namespace

Files changed:
- packages/db/package.json (v0.1.0 → v0.2.0)
- packages/db/src/index.ts (consolidated exports)
- packages/db/prisma/schema.prisma (merged schema)
- packages/db/prisma/seed.ts (updated for new schema)
- 17 consumer files updated

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/api/src/services/spamshield/spamshield.service.ts

@@ -1,4 +1,4 @@
-import { prisma, SpamFeedback } from '@shieldsai/shared-db';
+import { prisma, SpamFeedback } from '@shieldai/db';
 import { spamShieldEnv, SpamDecision, spamFeatureFlags, defaultScores, metadataLimits } from './spamshield.config';
 import { createHash } from 'crypto';
 import { spamAuditLogger, hashPhoneNumber } from './spamshield.audit-logger';