chore: fix lint issues in public.ts route file (#173)

- Reorder imports according to import-x/order (sibling then type groups)
- Add explicit Promise<void> return type to publicRoutes function
- Remove extra blank lines after imports

Author: rajesh-puripanda

apps/backend/src/routes/public.ts

@@ -1,8 +1,8 @@
-import type { FastifyContextConfig, FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
-import { generateQRBuffer, generateQRSvg } from '../utils/qr.js';
-import type { PlatformLink } from '@devcard/shared';
 import { getErrorMessage } from '../utils/error.util.js';
+import { generateQRBuffer, generateQRSvg } from '../utils/qr.js';
 
+import type { PlatformLink } from '@devcard/shared';
+import type { FastifyContextConfig, FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
 
 // ── QR size bounds ────────────────────────────────────────────────────────────
 // Enforced before any DB query or image allocation.  Values outside this range
@@ -75,7 +75,7 @@ interface CardLinkWithPlatform {
 }
 
 
-export async function publicRoutes(app: FastifyInstance) {
+export async function publicRoutes(app: FastifyInstance): Promise<void> {
   // ─── Public Profile ───
   app.get('/:username', {
     config: {