Add delete account endpoint and file encryption at rest

Delete Account (Plan #2):
- DELETE /api/auth/account/ with password or "DELETE" confirmation
- Cascade delete across 15+ tables in correct FK order
- Auth provider detection (email/apple/google) for /auth/me/
- File cleanup after account deletion
- Handler + repository tests (12 tests)

Encryption at Rest (Plan #3):
- AES-256-GCM envelope encryption (per-file DEK wrapped by KEK)
- Encrypt on upload, auto-decrypt on serve via StorageService.ReadFile()
- MediaHandler serves decrypted files via c.Blob()
- TaskService email image loading uses ReadFile()
- cmd/migrate-encrypt CLI tool with --dry-run for existing files
- Encryption service + storage service tests (18 tests)

docker-compose.yml

@@ -93,6 +93,9 @@ services:
       APNS_TOPIC: ${APNS_TOPIC}
       APNS_USE_SANDBOX: "${APNS_USE_SANDBOX:-false}"
       FCM_SERVER_KEY: ${FCM_SERVER_KEY}
+
+      # Storage encryption
+      STORAGE_ENCRYPTION_KEY: ${STORAGE_ENCRYPTION_KEY}
     volumes:
       - push_certs:/certs:ro
       - uploads:/app/uploads