api: API key authentication with rotation and grace period

- Add ApiKey Prisma model (keyHash, expiresAt, revokedAt)
- Protect /api/v1/* routes with Authorization: Bearer header check in hooks
- create rotateApiKey() utility: normal (48h grace) and emergency (immediate)
- Add Super-only /admin/api-keys page for key rotation with one-time reveal
- Fix roleId check by using parent layout's DB-fetched adminUser
- Add API Keys link to admin sidebar

prisma/schema.prisma

@@ -178,6 +178,15 @@ model LicenseKey {
   user   User    @relation(fields: [userId], references: [id])
 }
 
+model ApiKey {
+  id        String    @id @default(cuid())
+  keyPrefix String
+  keyHash   String    @unique
+  createdAt DateTime  @default(now())
+  expiresAt DateTime?
+  revokedAt DateTime?
+}
+
 model SubscriptionLevel {
   id            Int                                    @id @default(autoincrement())
   name          String