feat: implement R2 audio file management and rate limiting enhancements

- Add R2 client setup and audio upload functionality in lib/r2.ts.
- Create audio file cleanup functions in lib/r2-cleanup.ts to delete voice files associated with videos, projects, and workspaces.
- Enhance rate limiting in lib/rate-limit.ts with new action-specific limits and improved IP validation.
- Introduce a unified rate limit check function that returns a 429 response when limits are exceeded.
- Update package.json to include the AWS SDK for S3.

app/api/auth/[...nextauth]/route.ts

@@ -1,3 +1,12 @@
 import { handlers } from '@/lib/auth';
+import { rateLimit } from '@/lib/rate-limit';
 
-export const { GET, POST } = handlers;
+export const { GET } = handlers;
+
+// Wrap NextAuth POST with login rate limiting
+export async function POST(request: Request) {
+    const limited = await rateLimit(request, 'login');
+    if (limited) return limited;
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return handlers.POST(request as any);
+}