fix: implement chunked file uploading to bypass proxy size limits

backend/server.js

@@ -216,6 +216,61 @@ app.post('/api/upload', authenticate, upload.single('file'), (req, res) => {
   res.json({ url });
 });
 
+// 10b. Chunked Upload - Receive chunk
+app.post('/api/upload/chunk', authenticate, upload.single('file'), (req, res) => {
+  const { uploadId, chunkIndex, totalChunks } = req.body;
+  if (!req.file || !uploadId || !chunkIndex || !totalChunks) {
+    return res.status(400).json({ error: 'Missing chunk data' });
+  }
+
+  const tempDir = path.join(uploadsDir, 'temp', uploadId);
+  if (!fs.existsSync(tempDir)) {
+    fs.mkdirSync(tempDir, { recursive: true });
+  }
+
+  const chunkPath = path.join(tempDir, chunkIndex);
+  fs.renameSync(req.file.path, chunkPath);
+
+  res.json({ success: true });
+});
+
+// 10c. Chunked Upload - Complete
+app.post('/api/upload/complete', authenticate, (req, res) => {
+  const { uploadId, fileName, totalChunks } = req.body;
+  if (!uploadId || !fileName || !totalChunks) {
+    return res.status(400).json({ error: 'Missing completion data' });
+  }
+
+  const uniqueSuffix = Date.now() + '-' + Math.round(Math.random() * 1E9);
+  const finalFileName = uniqueSuffix + '-' + fileName;
+  const finalPath = path.join(uploadsDir, finalFileName);
+  const tempDir = path.join(uploadsDir, 'temp', uploadId);
+
+  try {
+    const writeStream = fs.createWriteStream(finalPath);
+    for (let i = 0; i < totalChunks; i++) {
+      const chunkPath = path.join(tempDir, i.toString());
+      if (!fs.existsSync(chunkPath)) {
+        throw new Error(`Chunk ${i} is missing`);
+      }
+      const data = fs.readFileSync(chunkPath);
+      writeStream.write(data);
+    }
+    writeStream.end();
+
+    // Clean up temp dir
+    fs.rmSync(tempDir, { recursive: true, force: true });
+    
+    const url = `/uploads/${finalFileName}`;
+    res.json({ url });
+  } catch (error) {
+    if (fs.existsSync(tempDir)) {
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    }
+    res.status(500).json({ error: error.message });
+  }
+});
+
 const PORT = process.env.PORT || 3005;
 app.listen(PORT, () => {
   console.log(`Backend server running on port ${PORT}`);