admin-panel: upgrade to ant-design-vue 4.2.6

- Bump ant-design-vue 3.2.20 -> 4.2.6, @ant-design/icons-vue 6.1.0 -> 7.0.1.
- ADV4 removed LESS theming (modifyVars) for CSS-in-JS design tokens: drop
  the vite.config.ts modifyVars block and the antd.less import; move the
  three tokens ant actually consumed (primary/link/border-radius) to
  App.vue's <a-config-provider :theme>.
- Delete src/assets/styles/ant.less (426 lines of hand-written RTL flips):
  ADV4 renders RTL natively via CSS logical properties given direction="rtl",
  which App.vue already sets. Preserve only the small residue ADV4 doesn't
  cover natively (upload filename LTR, select dropdown z-index, tabs nav
  direction) in a new rtl-overrides.css.
- Clean up the stale --primary/--accent token comment in utilities.less now
  that ant.less is gone.
- Verified: pnpm build (vue-tsc -b && vite build) passes with zero errors;
  the codebase already used v-model:open everywhere (no ADV3 visible prop
  usage to migrate).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/admin-panel/src/assets/styles/main.less

@@ -1,11 +1,21 @@
 // Style entry for admin-panel.
-// Order matters and mirrors legacy henza_admin/src/main.js:
-//   1. ant-design-vue's own less theme (compiled with the modifyVars in vite.config.ts)
-//   2. farsi.scss  -> font faces + global reset
-//   3. ara/ant.less -> RTL overrides layered on top of ant's defaults
-@import 'ant-design-vue/dist/antd.less';
+//
+// ant-design-vue 4 removed its LESS theme entirely (CSS-in-JS design tokens
+// replace modifyVars) — `ant-design-vue/dist/antd.less` no longer exists, so
+// it is no longer imported here; ADV4's runtime styles are injected by the
+// library itself. Primary/link/radius tokens now live in App.vue's
+// <a-config-provider :theme>.
+//
+// `ara/ant.less` (426 lines of hand-written RTL flips for float/margin/
+// transform) is also gone: ADV4 renders RTL natively via CSS logical
+// properties when direction="rtl" is set, which App.vue already does. The
+// small residue ADV4 does not cover lives in ./rtl-overrides.css.
+//
+// Remaining order:
+//   1. farsi.less     -> font faces + global reset
+//   2. rtl-overrides.css -> the few RTL rules ADV4 doesn't provide natively
+//   3. utilities.less -> the global utility layer replacing legacy's Tailwind
+//      build. Must come last so its card chrome layers over ant's own styles.
 @import './farsi.less';
-@import './ant.less';
-//   4. utilities.less -> the global utility layer replacing legacy's Tailwind
-//      build. Must come LAST so its card chrome layers over ant's own styles.
+@import './rtl-overrides.css';
 @import './utilities.less';