feat: responsive mobile UI across all pages

Global:
- Viewport meta already present; added -webkit-text-size-adjust: 100%
- Container padding reduces to 12px on mobile (was 24px)
- Smaller heading sizes (h1: 1.5rem, h2: 1.25rem)
- Buttons get min-height 40px for touch targets
- Inputs forced to 16px font-size to prevent iOS zoom
- Thinner scrollbar on mobile

Header:
- Logo text shrinks to 1rem on mobile, icon to 28px
- Header padding reduces to 12px

Library:
- Toolbar stacks vertically on mobile, full-width inputs
- Grid forced to 2 columns on narrow screens (480px), reduced gap

GameCard:
- Smaller info text, padding, badge on 480px screens

GameDetail:
- Cover section capped at 200px width on mobile
- Media thumbnails shrink to 160x90
- Scrape header stacks vertically with full-width buttons
- Edit rows stack vertically on mobile

Play:
- DOS container caps at 50vh on mobile, smaller border-radius
- Overlay text/icon sizes reduced, more compact layout

frontend/src/pages/Play.svelte

@@ -139,6 +139,7 @@
 
 <style>
   .play-page { padding: 16px 0; position: relative; }
+  @media (max-width: 640px) { .play-page { padding: 8px 0; } }
   .play-header {
     display: flex;
     justify-content: space-between;
@@ -177,6 +178,9 @@
     overflow: hidden;
     border: 1px solid var(--border);
   }
+  @media (max-width: 640px) {
+    .dos-container { aspect-ratio: 4/3; max-height: 50vh; border-radius: var(--radius-sm); }
+  }
   .dos-container :global(canvas) {
     width: 100% !important;
     height: 100% !important;
@@ -197,6 +201,13 @@
     border-radius: var(--radius);
     border: 1px dashed var(--border);
     margin-top: 4px;
+    padding: 20px;
+  }
+  @media (max-width: 640px) {
+    .overlay { top: 44px; border-radius: var(--radius-sm); padding: 16px; }
+    .overlay-icon { font-size: 2rem; }
+    .overlay h2 { font-size: 1rem; }
+    .overlay p { font-size: 0.85rem; }
   }
   .overlay-icon { font-size: 3rem; margin-bottom: 12px; }
   .overlay h2 {