task/31: Relay account whitelist + trust-gated access

## What was built
Full relay access control system: relay_accounts table, RelayAccountService,
trust hook integration, live policy enforcement, admin CRUD API, Timmy seed.

## DB change
`lib/db/src/schema/relay-accounts.ts` — new `relay_accounts` table:
  pubkey (PK, FK → nostr_identities.pubkey ON DELETE CASCADE),
  access_level ("none"|"read"|"write"), granted_by ("manual"|"auto-tier"),
  granted_at, revoked_at (nullable), notes. Pushed via `pnpm run push`.
`lib/db/src/schema/index.ts` — exports relay-accounts.

## RelayAccountService (`artifacts/api-server/src/lib/relay-accounts.ts`)
- getAccess(pubkey) → RelayAccessLevel (none if missing or revoked)
- grant(pubkey, level, reason, grantedBy) — upsert; creates nostr_identity FK
- revoke(pubkey, reason) — sets revokedAt, access_level → none
- syncFromTrustTier(pubkey, tier) — auto-promotes by tier; never downgrades manual grants
- list(opts) — returns all accounts, optionally filtered to active
- Tier→access map: new=none, established/trusted/elite=write (env-overridable)

## Trust hook (`artifacts/api-server/src/lib/trust.ts`)
recordSuccess + recordFailure both call syncFromTrustTier after writing tier.
Failure is caught + logged (non-blocking — trust flow never fails on relay error).

## Policy endpoint (`artifacts/api-server/src/routes/relay.ts`)
evaluatePolicy() now async: queries relay_accounts.getAccess(pubkey).
"write" → accept; "read"/"none"/missing → reject with clear message.
DB error → reject with "policy service error" (safe fail-closed).

## Admin routes (`artifacts/api-server/src/routes/admin-relay.ts`)
ADMIN_SECRET Bearer token auth (localhost-only fallback in dev; error log in prod).
GET  /api/admin/relay/accounts            — list all accounts
POST /api/admin/relay/accounts/:pk/grant  — grant (level + notes body)
POST /api/admin/relay/accounts/:pk/revoke — revoke (reason body)
pubkey validation: must be 64-char lowercase hex.

## Startup seed (`artifacts/api-server/src/index.ts`)
On every startup: grants Timmy's own pubkeyHex "write" access ("manual").
Idempotent upsert — safe across restarts.

## Smoke test results (all pass)
- Timmy pubkey → accept ✓; unknown pubkey → reject ✓
- Admin grant → accept ✓; admin revoke → reject ✓; admin list shows accounts ✓
- TypeScript: 0 errors in API server + lib/db

artifacts/api-server/src/routes/index.ts

@@ -13,6 +13,7 @@ import worldRouter from "./world.js";
 import identityRouter from "./identity.js";
 import estimateRouter from "./estimate.js";
 import relayRouter from "./relay.js";
+import adminRelayRouter from "./admin-relay.js";
 
 const router: IRouter = Router();
 
@@ -24,6 +25,7 @@ router.use(bootstrapRouter);
 router.use(sessionsRouter);
 router.use(identityRouter);
 router.use(relayRouter);
+router.use(adminRelayRouter);
 router.use(demoRouter);
 router.use(testkitRouter);
 router.use(uiRouter);