feat: LinkedIn video upload support (linkedin_upload_video tool + REST route)

Implements full 4-step LinkedIn Videos API flow: download from public URL,
initialize upload, 4MB chunk PUT with ETag collection, finalize, poll until
AVAILABLE, then publish via POST /rest/posts reading post ID from x-restli-id.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/index.ts

@@ -755,6 +755,16 @@ app.post('/api/linkedin/post', requireAuth, async (req, res) => {
   }
 });
 
+app.post('/api/linkedin/video', requireAuth, async (req, res) => {
+  try {
+    const { video_url, text, visibility, account } = req.body as Record<string, unknown>;
+    const result = await handleToolCall('linkedin_upload_video', { video_url, text, visibility, account });
+    res.json(result);
+  } catch (err) {
+    res.status(500).json({ error: String(err) });
+  }
+});
+
 app.post('/api/linkedin/search-connections', requireAuth, async (req, res) => {
   const { keywords, account } = req.body as Record<string, unknown>;
   try {