fix(keys): add DB fallback to updateEmailByCustomer, updateKeyEmail, and recover route (BUG-108, BUG-109, BUG-110)

- updateEmailByCustomer: DB fallback when stripe_customer_id not in cache
- updateKeyEmail: DB fallback when key not in cache
- POST /v1/recover: DB fallback when email not in cache (was only on verify)
- 6 TDD tests added (keys-email-update.test.ts, recover-initial-db-fallback.test.ts)
- 547 tests total, all passing

src/routes/recover.ts

@@ -69,6 +69,18 @@ router.post("/", recoverLimiter, async (req: Request, res: Response) => {
   const userKey = keys.find(k => k.email === cleanEmail);
   
   if (!userKey) {
+    // DB fallback: cache may be stale in multi-replica setups
+    const dbResult = await queryWithRetry(
+      "SELECT key FROM api_keys WHERE email = $1 LIMIT 1",
+      [cleanEmail]
+    );
+    if (dbResult.rows.length > 0) {
+      const pending = await createPendingVerification(cleanEmail);
+      sendVerificationEmail(cleanEmail, pending.code).catch(err => {
+        logger.error({ err, email: cleanEmail }, "Failed to send recovery email");
+      });
+      logger.info({ email: cleanEmail }, "recover: cache miss, sent recovery via DB fallback");
+    }
     res.json({ status: "recovery_sent", message: "If an account exists for this email, a verification code has been sent." });
     return;
   }