feat: Slack platform + Claude-powered chat support widget

- Add Slack as customer-facing messaging platform (client, 4 MCP tools, dashboard card)
- Add /api/chat endpoint powered by Claude Haiku with SquareMCP system prompt
- Add embeddable chat-widget.js injected into all 3 sites (docs, app, www)
- Add ANTHROPIC_API_KEY, serve product/ as static files
- Update Platform type to include slack

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

src/index.ts

@@ -36,6 +36,7 @@ import { getAllPlatformHealth } from './multitenancy/platform-health.js';
 import { deliverWebhook, isValidWebhookUrl } from './webhooks/delivery.js';
 import { notifyNewPilotRequest } from './notifications/index.js';
 import redis from './redis.js';
+import { handleChat, type ChatMessage } from './chat.js';
 
 const app = express();
 app.use(cookieParser());
@@ -57,6 +58,7 @@ app.use(express.urlencoded({ extended: true }));
 
 // ── Static files (videos, assets) ──────────────────────────────────────────
 app.use('/public', express.static('/vaults/public'));
+app.use(express.static(new URL('../../product', import.meta.url).pathname));
 
 // ── Config ─────────────────────────────────────────────────────────────────
 const PORT = process.env.PORT ?? 3456;
@@ -1978,6 +1980,22 @@ app.post('/api/facebook/video', requireAuth, async (req, res) => {
   }
 });
 
+// ── Chat widget endpoint ────────────────────────────────────────
+app.post('/api/chat', async (req, res) => {
+  const { messages } = req.body as { messages?: ChatMessage[] };
+  if (!Array.isArray(messages) || messages.length === 0) {
+    res.status(400).json({ error: 'messages array required' });
+    return;
+  }
+  try {
+    const reply = await handleChat(messages);
+    res.json({ reply });
+  } catch (err) {
+    console.error('[chat] error:', (err as Error).message);
+    res.status(500).json({ error: 'Chat unavailable' });
+  }
+});
+
 // ── TikTok REST endpoints ───────────────────────────────────────
 app.get('/api/tiktok/profile', requireAuth, async (req, res) => {
   const account = req.query.account as string | undefined;