fix: Container width setting now applies correctly + Rail Ads improvements

- Fix container width not applying: css-global-responsive.css now uses
  CSS variable --roi-container-width instead of hardcoded values
- Add 8 Rail format options: slim-small (160x300), slim-medium (160x400),
  slim-large (160x500), skyscraper (160x600), slim-xlarge (160x700),
  wide-skyscraper (160x800), half-page (300x600), large-skyscraper (300x1050)
- Change rail_top_offset from text input to select with preset values
- Fix Rail Ads JavaScript positioning (moved after HTML, added retries)
- ThemeSettingsRenderer now always outputs CSS variables for layout

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Assets/css/css-global-responsive.css

@@ -246,31 +246,12 @@
         font-size: 24px;
     }
 
-    .container {
-        max-width: 1140px;
-    }
-
-    .container-lg {
-        max-width: 1280px;
-    }
-
-    .container-xl {
-        max-width: 1400px;
-    }
-}
-
-/* XXL devices (1400px and up) */
-@media (min-width: 1400px) {
-    .container {
-        max-width: 1320px;
-    }
-
-    .container-xl {
-        max-width: 1500px;
-    }
-
+    /* Container width uses CSS variable from Theme Settings */
+    .container,
+    .container-lg,
+    .container-xl,
     .container-xxl {
-        max-width: 1700px;
+        max-width: var(--roi-container-width, 1320px);
     }
 }