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/lib/Header.svelte

@@ -40,6 +40,9 @@
     align-items: center;
     justify-content: space-between;
   }
+  @media (max-width: 640px) {
+    .header-inner { padding: 0 12px; }
+  }
   .logo {
     display: flex;
     align-items: center;
@@ -58,6 +61,10 @@
     letter-spacing: 0.15em;
     animation: phosphor-pulse 3s ease-in-out infinite;
   }
+  @media (max-width: 640px) {
+    .logo-text { font-size: 1rem; letter-spacing: 0.1em; }
+    .logo-icon { width: 28px; height: 28px; }
+  }
   nav {
     display: flex;
     gap: 8px;