feat(01-03): register rankingRouter in appRouter

- Import rankingRouter from './ranking'
- Add ranking: rankingRouter after filtering entry
- Build verified: passes typecheck and production build

src/server/routers/_app.ts

@@ -26,6 +26,7 @@ import { logoRouter } from './logo'
 import { applicationRouter } from './application'
 import { mentorRouter } from './mentor'
 import { filteringRouter } from './filtering'
+import { rankingRouter } from './ranking'
 import { specialAwardRouter } from './specialAward'
 import { notificationRouter } from './notification'
 // Feature expansion routers
@@ -83,6 +84,7 @@ export const appRouter = router({
   application: applicationRouter,
   mentor: mentorRouter,
   filtering: filteringRouter,
+  ranking: rankingRouter,
   specialAward: specialAwardRouter,
   notification: notificationRouter,
   // Feature expansion routers