feat(mobile): mobile-responsive UI — bottom tab bar, bottom-sheet dialogs, PWA

All changes are gated behind max-md:/md:hidden so the >=768px desktop layout is untouched (verified with lint + build + live checks at 375px).

- globals.css: one mobile block — 16px inputs (no iOS auto-zoom), units sidebar stacks above content, wizard item rows become 2-col (text fields full-width, delete button full-width), dd-panels / flow diagram / conv-form stack, larger touch targets
- ui/dialog.tsx: dialogs become full-width bottom sheets on mobile (all modals inherit it); desktop keeps the centered dialog
- Header: sticky on mobile only + PageLayout bottom clearance
- New MobileTabBar: role-aware bottom tabs (office admin/manager, inventory PM, inventory admin); hidden on /wizard
- Wizard step 4: TouchSensor (150ms delay) so touch drag works without stealing scroll
- JalaliDatePicker: dropdown capped to viewport; bigger day cells and time inputs on mobile
- PWA: manifest.webmanifest + 192/512 icons (scripts/gen-pwa-icons.ps1) + theme-color/manifest links in index.html
- New docs/mobile-responsive.md documenting the full change set

frontend/src/pages/Suppliers/CategoryPage.tsx

@@ -109,7 +109,7 @@ export function CategoryPage() {
           <h4>
             <Plus className="me-1 inline h-4 w-4 text-accent" /> افزودن تأمین‌کننده‌ی جدید
           </h4>
-          <div className="grid max-w-2xl grid-cols-2 gap-3">
+          <div className="grid max-w-2xl grid-cols-2 gap-3 max-md:grid-cols-1">
             <div className="field">
               <label>نام تأمین‌کننده *</label>
               <Combobox