docs: add web dashboard documentation (#8864)

- New docs page: user-guide/features/web-dashboard.md covering
  quick start, prerequisites, all three pages (Status, Config, API Keys),
  the /reload slash command, REST API endpoints, CORS config, and
  development workflow
- Added 'Management' category in sidebar for web-dashboard
- Added 'hermes web' to CLI commands reference with options table
- Added '/reload' to slash commands reference (both CLI and gateway tables)

website/sidebars.ts

@@ -73,6 +73,13 @@ const sidebars: SidebarsConfig = {
             'user-guide/features/tts',
           ],
         },
+        {
+          type: 'category',
+          label: 'Management',
+          items: [
+            'user-guide/features/web-dashboard',
+          ],
+        },
         {
           type: 'category',
           label: 'Advanced',