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>

product/app/app.js

@@ -103,6 +103,15 @@ const PLATFORM_CONFIG = {
     ],
     help: 'From Meta Business Settings → WhatsApp → API Setup. You need a verified business phone number.',
   },
+  slack: {
+    name: 'Slack',
+    type: 'token',
+    fields: [
+      { key: 'accessToken', label: 'Bot Token', type: 'password' },
+      { key: 'channelId', label: 'Default Channel ID', type: 'text' },
+    ],
+    help: 'Go to api.slack.com/apps → Create App → OAuth & Permissions → install to workspace. Copy the Bot User OAuth Token.',
+  },
   email: {
     name: 'Email',
     type: 'token',
@@ -403,7 +412,7 @@ async function loadInvoices() {
 const PLATFORM_COLORS = {
   email: '#ea4335', linkedin: '#0a66c2', twitter: '#000000',
   instagram: '#e1306c', facebook: '#1877f2', tiktok: '#010101',
-  whatsapp: '#25d366', telegram: '#0088cc', discord: '#5865f2',
+  whatsapp: '#25d366', telegram: '#0088cc', discord: '#5865f2', slack: '#4a154b',
   snapchat: '#fffc00', obsidian: '#7c3aed',
 };