feat(home): add compact home page preset to avoid abuse classification

- Add compact_home_enabled setting to provide a minimal landing page
- Preserves custom home_content priority over compact mode
- Renders only site identity, navigation, and login/dashboard link
- Avoids marketing copy that triggers anti-fraud systems
- Includes focused backend/frontend tests and i18n support

Fixes #5065

frontend/src/api/admin/settings.ts

@@ -440,6 +440,7 @@ export interface SystemSettings {
   contact_info: string;
   doc_url: string;
   home_content: string;
+  compact_home_enabled: boolean;
   hide_ccs_import_button: boolean;
   table_default_page_size: number;
   table_page_size_options: number[];
@@ -752,6 +753,7 @@ export interface UpdateSettingsRequest {
   contact_info?: string;
   doc_url?: string;
   home_content?: string;
+  compact_home_enabled?: boolean;
   hide_ccs_import_button?: boolean;
   table_default_page_size?: number;
   table_page_size_options?: number[];