feat: mobile-first responsive overhaul — safe areas, touch targets, bottom sheet, bottom nav

Viewport:
- Add `viewport` export with `viewport-fit=cover` (enables CSS safe-area-inset-*
  on bezel-less iOS/Android) and `interactive-widget=resizes-content` (prevents
  layout jumps from virtual keyboard open/close)

iOS zoom prevention:
- input.tsx, textarea.tsx: change text-sm (14px) → text-base sm:text-sm (16px)
  on mobile; iOS Safari auto-zooms any input with font-size < 16px

Touch targets:
- button.tsx: default h-10 → h-11 (44px), sm h-8 → h-9 (36px), icon h-10→h-11
  matching the 44×44px iOS HIG and WCAG 2.5.5 minimum
- Add touch-manipulation to buttons, inputs, textarea to eliminate 300ms tap delay

Dialog → mobile bottom sheet:
- On mobile (< 640px): anchored to bottom with full width, rounded top corners,
  slide-in-from-bottom / slide-out-to-bottom animation, drag handle affordance,
  max-h-[90svh] + overflow-y-auto to prevent viewport overflow
- Safe area padding: pb-[max(1.25rem,env(safe-area-inset-bottom))]
- On desktop (sm+): unchanged centered modal with zoom animation
- Close button gets a 32×32 tap area on mobile

Mobile navigation:
- New bottom-nav.tsx: persistent 3-tab bottom bar (مسیر/مرکز/لیگ) shown below
  md: breakpoint, hidden on desktop; 56px height + safe-area-inset-bottom;
  active tab gets heavier stroke and scale
- Only shown for authenticated non-admin users
- app-shell.tsx: injects BottomNav; main content gets dynamic padding-bottom to
  clear the bar (56px + safe area) on mobile, reverts to py-10 on md:
- Footer: safe-area-inset-bottom padding so content clears iPhone home indicator

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/ui/input.tsx

@@ -33,7 +33,8 @@ const Input = React.forwardRef<HTMLInputElement, React.InputHTMLAttributes<HTMLI
         type={type}
         className={cn(
           // Fixed height + symmetric vertical padding; avoid clipping Vazirmatn descenders.
-          "box-border h-11 w-full rounded-lg border border-input bg-card px-3.5 py-0 font-sans text-sm font-medium leading-none outline-none transition-colors placeholder:font-sans placeholder:font-medium placeholder:text-muted-foreground focus-visible:ring-2 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
+          // text-base (16px) prevents iOS Safari auto-zoom on focus; sm: downsizes on desktop
+          "box-border h-11 w-full rounded-lg border border-input bg-card px-3.5 py-0 font-sans text-base sm:text-sm font-medium leading-none outline-none transition-colors touch-manipulation placeholder:font-sans placeholder:font-medium placeholder:text-muted-foreground focus-visible:ring-2 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
           latin && "font-latin placeholder:font-latin",
           className
         )}