Fix TypeScript and lint errors

- Add missing reqHeaders/resHeaders to webauthn test context
- Fix Session.id type from number to string in test
- Remove unnecessary Number() conversion in countOwners

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api-server/src/__tests__/e2e/webauthn.test.ts

@@ -49,6 +49,8 @@ function createAPIContext(): APIContext {
     origin: TEST_RP.origin,
     allowedOrigins: [...TEST_RP.allowedOrigins],
     rpName: TEST_RP.rpName,
+    reqHeaders: new Headers(),
+    resHeaders: new Headers(),
   };
 }
 
@@ -69,7 +71,7 @@ function createAuthenticatedContext(
       isSuperuser: false,
     },
     session: {
-      id: 1,
+      id: "1",
       trustedMode: false,
       createdAt: new Date(),
     },