fix(frontend): drop 12px font pin on header icon cards to match reference

The reference theme renders header slider icon cards on the bootstrap
14px body baseline (title .em12 -> 16.8px, desc 14px). A local
.header-slider-card .icon-cover-card { font-size: 12px } override shrank
text to 14.4/12px, making AKSRT cards visibly smaller than the reference.
Remove the pin from base.css and the public bundle; container gutter
restoration stays.

tests/widget-system/icon-card-contract.test.cjs

@@ -33,9 +33,16 @@ test('homepage horizontal cards render fully from legacy CSS with no dedicated s
   assert.equal(fs.existsSync(path.join(root, 'assets/css/frontend/header-cards.css')), false);
   assert.doesNotMatch(baseCss, /\.icon-cover-card\.aksrt-icon-cover-card/);
   assert.doesNotMatch(baseCss, /\.header-components-card/);
-  assert.match(
+  // Reference theme pins no font-size on header cards: text inherits the
+  // bootstrap 14px baseline (title .em12 -> 16.8px). A local 12px override
+  // made AKSRT cards visually smaller than the reference.
+  assert.doesNotMatch(
     baseCss,
-    /\.header-slider-card\s+\.icon-cover-card\s*\{[^}]*font-size:\s*12px/s,
+    /\.header-slider-card\s+\.icon-cover-card\s*\{[^}]*font-size/s,
+  );
+  assert.doesNotMatch(
+    read('assets/css/build/public.css'),
+    /\.header-slider-card\s+\.icon-cover-card\s*\{[^}]*font-size/s,
   );
   assert.doesNotMatch(scripts, /header-cards/);
   assert.doesNotMatch(widgetCss, /aksrt-widget-icon-cards \.icon-cover-card/);