feat(mobile): responsive Phase 1+2 — global small-phone rules + area fixes

All changes are mobile-only (max-width media queries); desktop unchanged.

Global (systemic):
- forms.css: all .admin-form-row* grids stack to 1 column at <=480px (fixes
  detail-page info grids, settings forms, modal forms staying 2-up on phones).
- components.css: .admin-kpi-4/-3 stat grids collapse to 1 column at <=480px.
- tables.css: row-action icons get 44px touch targets at <=768px.
- datepicker.css: constrain the date-picker popper to the viewport at <=480px.
- filemanager.css: toolbar wraps, new-folder input full-width, breadcrumb scrolls.

Area specifics:
- offers.css: Quill picker dropdowns kept on-screen (max-width) at <=480px.
- invoices.css: month-nav wraps + 44px touch targets at <=640px.
- attendance.css: Leaflet map height scales with viewport; clock-card padding
  tightened at <=480px.

Audit confirmed all data tables (warehouse incl.) are already wrapped in the
scroll container, so no table overflow/markup changes were needed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/components.css

@@ -845,7 +845,9 @@
 }
 
 @media (max-width: 480px) {
-  .admin-kpi-grid {
+  .admin-kpi-grid,
+  .admin-kpi-4,
+  .admin-kpi-3 {
     grid-template-columns: 1fr;
   }
 }