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/public/manifest.webmanifest

@@ -0,0 +1,33 @@
+{
+  "name": "دفترچه تأمین — سامانه تدارکات و انبار",
+  "short_name": "دفترچه تأمین",
+  "description": "سامانه تدارکات و مدیریت انبار پروژه‌های ساختمانی",
+  "dir": "rtl",
+  "lang": "fa",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "portrait",
+  "background_color": "#f3f5f9",
+  "theme_color": "#4f46e5",
+  "icons": [
+    {
+      "src": "/icons/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    }
+  ]
+}