Add mobile responsiveness + PWA support

Mobile (768px):
- Tab bar: horizontal scroll with momentum, hidden scrollbar
- Header: compact layout, smaller fonts
- Tables: horizontal scroll, hide-mobile class for less important cols
- Modals: bottom-sheet style, full width
- Touch targets: min-height 36px for buttons/selects
- Toolbar: stacks vertically
- Stat cards: compact

Small phone (480px):
- Even more compact header and tabs
- Smaller table cells
- iOS zoom prevention (16px font on inputs)

PWA:
- manifest.json for Add to Home Screen
- apple-mobile-web-app-capable meta tags
- theme-color for status bar
- overscroll-behavior: none (prevent pull-to-refresh)

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

manifest.json

@@ -0,0 +1,22 @@
+{
+    "name": "Noxus HUB",
+    "short_name": "HUB",
+    "description": "Noxus HUB - Hallintapaneeli",
+    "start_url": "/",
+    "display": "standalone",
+    "orientation": "any",
+    "background_color": "#0f3460",
+    "theme_color": "#0f3460",
+    "icons": [
+        {
+            "src": "icon-192.png",
+            "sizes": "192x192",
+            "type": "image/png"
+        },
+        {
+            "src": "icon-512.png",
+            "sizes": "512x512",
+            "type": "image/png"
+        }
+    ]
+}