refactor(frontend) : make page headers and filters sticky across all pages

Wrap title + filters in a sticky container (top-8 sm:top-12, z-20, bg-white)
on all pages for consistent scroll behavior. Also fix SidebarTimer icon
visibility when sidebar is collapsed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/reference.php

@@ -467,7 +467,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *     },
  *     disallow_search_engine_index?: bool|Param, // Enabled by default when debug is enabled. // Default: true
  *     http_client?: bool|array{ // HTTP Client configuration
- *         enabled?: bool|Param, // Default: false
+ *         enabled?: bool|Param, // Default: true
  *         max_host_connections?: int|Param, // The maximum number of connections to a single host.
  *         default_options?: array{
  *             headers?: array<string, mixed>,