fix(navigation): restore the reference 8px radius and unclip the mega menu

Traced against the running site (docker theme at AKSRT-theme) with real
computed styles:

- theme_main_radius defaulted to 12, so --main-radius was 12px and every
  dropdown panel, card and button was rounder than the reference, which
  sets 8px. Default is now 8 in the runtime reader and both schemas.
- The public bundle loads after main.min.css. Its bare img rule replaced
  the inline image baseline the menu relies on, and html{overflow-x} made
  the root a clipping context that crops the fixed senior mega menu.
  Reset is now scoped to content; the horizontal-overflow guard is on body.
- The senior mega menu renders a .container inside the dropdown where the
  reference keeps Bootstrap's 15px gutter; the padding-free site-shell
  .container rule stripped it, running the card/link grid to the edges.

Rebuilt public.css / public.min.css and the admin SPA.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

assets/css/frontend/base.css

@@ -103,6 +103,17 @@ main.container,
   --bs-gutter-y: 0;
 }
 
+/* The senior mega menu renders its own .container inside the dropdown, where
+ * the reference keeps Bootstrap's 15px gutter and the plain content max-width.
+ * The padding-free site-shell rule above would otherwise strip it and let the
+ * card/link grid run flush to the panel edges. */
+.navbar-top .sub-menu.senior-submenu > .container,
+.mobile-navbar .sub-menu.senior-submenu > .container {
+  max-width: var(--mian-max-width);
+  padding-right: 15px;
+  padding-left: 15px;
+}
+
 /* Header multifunc icon cards must align with the main content edges:
  * the global .container is padding-free at >=992px (dual-column float
  * math), so the card container gets no extra gutter either. The