docs(mobile-client): update features list in sidebar

- Reorder 'Headline Details' and 'Entity Details' items
- Add 'Ad System' feature link
- Move 'Headlines Feed' above 'Headline Details' for better organization

Author: fulleni

astro.config.mjs

@@ -161,9 +161,10 @@ export default defineConfig({
 								{ label: 'Overview', link: '/mobile-client/features/' },
 								{ label: 'Account', link: '/mobile-client/features/account' },
 								{ label: 'Authentication', link: '/mobile-client/features/authentication' },
-								{ label: 'Entity Details', link: '/mobile-client/features/entity-details' },
-								{ label: 'Headline Details', link: '/mobile-client/features/headline-details' },
+								{ label: 'Ad System', link: '/mobile-client/features/ad-system' },
 								{ label: 'Headlines Feed', link: '/mobile-client/features/headlines-feed' },
+								{ label: 'Headline Details', link: '/mobile-client/features/headline-details' },
+								{ label: 'Entity Details', link: '/mobile-client/features/entity-details' },
 								{ label: 'Search', link: '/mobile-client/features/search' },
 								{ label: 'Settings', link: '/mobile-client/features/settings' },
 								{ label: 'Status Pages', link: '/mobile-client/features/status-pages' },