feat(nav): complete remaining zibll parity (search, i18n, senior menus, CSS)

- Remove obsolete dual-path nav CSS; add utilities + language dropdown styles
- Wire header/mobile translate switcher from i18n config
- Layout-2 inline search hot keywords panel; nav_folding on resize
- NavMenuOptions JSON editors for graphic_card / multi_column_links
- Section-navs zibll posts-nav-lists; page-navs enqueue; mobile article TOC box
- SPA/PHP user-card publish type; rebuild admin assets

assets/css/frontend/nav.css

@@ -2,10 +2,7 @@
 @import url("nav/zib-navbar-core.css");
 @import url("nav/zib-mobile-navbar.css");
 @import url("nav/zib-senior-submenu.css");
-@import url("nav/dark-mode-submenu.css");
-@import url("nav/dark-mode-mega-menu.css");
+@import url("nav/zib-utilities.css");
 @import url("nav/header-menu-buttons.css");
 @import url("nav/header-userbox.css");
-@import url("nav/menu-item-icon.css");
-@import url("nav/menu-item-badge.css");
-@import url("nav/hover-effects.css");
+@import url("nav/dark-mode-submenu.css");