feat(mana-auth): encryption vault — phase 2 (server-side master key custody)

Adds the server side of the per-user encryption vault. Phase 1 shipped
the client foundation (no-op while every table is enabled:false). This
commit lets the client actually fetch a master key when Phase 3 flips
the registry switches.

Schema (Drizzle + raw SQL migration)
  - auth.encryption_vaults: per-user wrapped MK + IV + format version +
    kek_id stamp + created/rotated timestamps. PK = user_id, ON DELETE
    CASCADE so account deletion wipes the vault.
  - auth.encryption_vault_audit: append-only trail of init/fetch/rotate
    actions with IP, user-agent, HTTP status, free-form context.
  - sql/002_encryption_vaults.sql: idempotent CREATE TABLE + ENABLE +
    FORCE row-level security with a `current_setting('app.current_user_id')`
    policy on both tables. FORCE makes the policy apply to the table
    owner too — no bypass via grants.

KEK loader (services/encryption-vault/kek.ts)
  - Loads a 32-byte AES-256 KEK from the MANA_AUTH_KEK env var (base64).
  - Production: missing or wrong-length input is fatal at boot.
  - Development: 32-zero-byte fallback so contributors can run the
    service without provisioning a secret. Logs a loud warning.
  - wrapMasterKey / unwrapMasterKey use Web Crypto AES-GCM-256 over the
    raw 32-byte MK with a fresh 12-byte IV per wrap. Returns base64
    pair for storage.
  - generateMasterKey + activeKekId helpers used by the service.
  - Future migration to KMS / Vault: only loadKek() changes; the
    kek_id stamp on each row tracks which KEK produced it.

EncryptionVaultService (services/encryption-vault/index.ts)
  - init(userId): idempotent — returns existing MK or mints a new one.
  - getMasterKey(userId): unwraps the stored MK; throws VaultNotFoundError
    on no-row so the route can return 404 cleanly.
  - rotate(userId): mints fresh MK, replaces wrap. Caller is on the
    hook for re-encryption — destructive by design.
  - withUserScope(userId, fn): wraps every read/write in a Drizzle
    transaction with set_config('app.current_user_id', userId, true)
    so the RLS policy admits only the matching row. Empty userId is
    rejected up-front.
  - writeAudit() appends a row to encryption_vault_audit on every
    action including failures, so probing attempts leave a trail.

Routes (routes/encryption-vault.ts)
  - POST /api/v1/me/encryption-vault/init  — idempotent bootstrap
  - GET  /api/v1/me/encryption-vault/key   — fetch the active MK
  - POST /api/v1/me/encryption-vault/rotate — destructive rotation
  - All return base64-encoded master key bytes plus formatVersion +
    kekId. JWT-protected via the existing /api/v1/me/* middleware.
  - readAuditContext() pulls X-Forwarded-For + User-Agent off the
    request for the audit row.

Bootstrap (index.ts)
  - loadKek() runs at top-level await before any route can fire so a
    misconfigured KEK fails closed at boot, never at request time.
  - encryptionVaultService is mounted under /api/v1/me/encryption-vault
    so it inherits the existing JWT middleware and shows up next to the
    GDPR self-service endpoints.

Tests (services/encryption-vault/kek.test.ts)
  - 11 Bun-test cases covering: KEK load (happy path, wrong length,
    idempotent, before-load guard), generateMasterKey randomness,
    wrap/unwrap roundtrip, IV uniqueness across repeated wraps,
    wrong-MK-length rejection, tampered-ciphertext rejection,
    wrong-length IV rejection, wrong-KEK rejection.
  - Service-level integration tests deferred — they need a real
    Postgres for the RLS behaviour, set up via existing mana-sync
    test pattern in CI.

Config + env
  - .env.development gains MANA_AUTH_KEK= (empty → dev fallback)
    with a comment explaining the production requirement.
  - services/mana-auth/package.json gains "test": "bun test".

Verified: 11/11 KEK tests passing, 31/31 Phase 1 client tests still
passing, only pre-existing TS errors remain in mana-auth (auth.ts:281
forgetPassword + api-keys.ts:50 insert overload — both unrelated).

Phase 3: client wires the MemoryKeyProvider to GET /encryption-vault/key
on login, flips registry entries to enabled:true table by table, and
extends the Dexie hooks to call wrapValue/unwrapValue on configured
fields.
Phase 4: settings UI for lock state, key rotation, recovery code opt-in.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

services/mana-auth/src/index.ts

@@ -17,10 +17,13 @@ import { SecurityEventsService, AccountLockoutService } from './services/securit
 import { SignupLimitService } from './services/signup-limit';
 import { ApiKeysService } from './services/api-keys';
 import { UserDataService } from './services/user-data';
+import { EncryptionVaultService } from './services/encryption-vault';
+import { loadKek } from './services/encryption-vault/kek';
 import { createAuthRoutes } from './routes/auth';
 import { createGuildRoutes } from './routes/guilds';
 import { createApiKeyRoutes, createApiKeyValidationRoute } from './routes/api-keys';
 import { createMeRoutes } from './routes/me';
+import { createEncryptionVaultRoutes } from './routes/encryption-vault';
 import { createSettingsRoutes } from './routes/settings';
 import { createAdminRoutes } from './routes/admin';
 
@@ -30,12 +33,18 @@ const config = loadConfig();
 const db = getDb(config.databaseUrl);
 const auth = createBetterAuth(config.databaseUrl);
 
+// Load the Key Encryption Key before any vault operation can run.
+// Top-level await is supported by Bun. Throws if MANA_AUTH_KEK is
+// missing in production or malformed in any environment.
+await loadKek(config.encryptionKek);
+
 // Initialize services
 const security = new SecurityEventsService(db);
 const lockout = new AccountLockoutService(db);
 const signupLimit = new SignupLimitService(db);
 const apiKeysService = new ApiKeysService(db);
 const userDataService = new UserDataService(db, config);
+const encryptionVaultService = new EncryptionVaultService(db);
 
 // ─── App ────────────────────────────────────────────────────
 
@@ -83,6 +92,11 @@ app.route('/api/v1/api-keys', createApiKeyValidationRoute(apiKeysService));
 app.use('/api/v1/me/*', jwtAuth(config.baseUrl));
 app.route('/api/v1/me', createMeRoutes(userDataService));
 
+// ─── Encryption vault (per-user master key custody) ────────
+// Mounted under /me so it inherits the JWT middleware above and shows
+// up in the same self-service surface as the GDPR endpoints.
+app.route('/api/v1/me/encryption-vault', createEncryptionVaultRoutes(encryptionVaultService));
+
 // ─── Settings ──────────────────────────────────────────────
 
 app.use('/api/v1/settings/*', jwtAuth(config.baseUrl));