fix: improve Android tablet keyboard-safe layout

Use dynamic viewport sizing and keyboard-aware spacing to keep new-game inputs and navigation reachable in PWA landscape mode on Android tablets. Refs #30.

Made-with: Cursor

src/styles/index.css

@@ -3,17 +3,13 @@
     margin: 0;
     padding: 0;
     box-sizing: border-box;
-    -webkit-touch-callout: none;
-    -webkit-user-select: none;
-    -khtml-user-select: none;
-    -moz-user-select: none;
-    -ms-user-select: none;
-    user-select: none;
     -webkit-tap-highlight-color: transparent;
 }
 
 /* Design system tokens */
 :root {
+    --app-height: 100dvh;
+    --keyboard-offset: 0px;
     /* Colors */
     --color-primary: #ff9800;
     --color-primary-hover: #ffa726;
@@ -87,7 +83,7 @@
 
 html, body {
     height: 100%;
-    overflow: hidden;
+    min-height: 100%;
 }
 
 body {
@@ -98,6 +94,13 @@ body {
     line-height: 1.5;
     -webkit-font-smoothing: antialiased;
     -moz-osx-font-smoothing: grayscale;
+    min-height: var(--app-height);
+}
+
+button, .btn, .button {
+    -webkit-user-select: none;
+    user-select: none;
+    -webkit-touch-callout: none;
 }
 
 /* Improved input styling for better tablet experience */