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/upload/audio/[filename]/route.ts

@@ -0,0 +1,58 @@
+import { NextResponse } from 'next/server';
+import { r2Client, R2_BUCKET_NAME } from '@/lib/r2';
+import { GetObjectCommand } from '@aws-sdk/client-s3';
+
+// Only allow UUID filenames with safe extensions
+const SAFE_FILENAME = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\.[a-z0-9]+$/i;
+
+export async function GET(
+  _request: Request,
+  { params }: { params: Promise<{ filename: string }> }
+) {
+  try {
+    const { filename } = await params;
+
+    // Validate filename to prevent path traversal
+    if (!SAFE_FILENAME.test(filename)) {
+      return NextResponse.json({ error: 'Invalid filename' }, { status: 400 });
+    }
+
+    const key = `voice/${filename}`;
+
+    const response = await r2Client.send(
+      new GetObjectCommand({
+        Bucket: R2_BUCKET_NAME,
+        Key: key,
+      })
+    );
+
+    if (!response.Body) {
+      return NextResponse.json({ error: 'File not found' }, { status: 404 });
+    }
+
+    const contentType = response.ContentType || 'audio/webm';
+    const contentLength = response.ContentLength;
+
+    // Stream the response body directly instead of buffering in memory
+    const stream = response.Body.transformToWebStream();
+
+    return new NextResponse(stream, {
+      status: 200,
+      headers: {
+        'Content-Type': contentType,
+        ...(contentLength ? { 'Content-Length': String(contentLength) } : {}),
+        'Cache-Control': 'public, max-age=31536000, immutable',
+      },
+    });
+  } catch (error: unknown) {
+    const errorName = error instanceof Error ? error.name : '';
+    if (errorName === 'NoSuchKey') {
+      return NextResponse.json({ error: 'File not found' }, { status: 404 });
+    }
+    console.error('Error serving audio:', error);
+    return NextResponse.json(
+      { error: 'Failed to retrieve audio' },
+      { status: 500 }
+    );
+  }
+}