fix: enable touch panning and prevent page scroll on mobile

- Add touch-action: none on canvas to prevent browser scroll hijack
- Single-finger touch on empty canvas now triggers pan (pointerType check)
- Fix page bounce on mobile with position: fixed and 100dvh height

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/App.jsx

@@ -91,10 +91,17 @@ export default function App({ onSwitchToGame }) {
       state.panStart = { x: e.clientX - state.camX, y: e.clientY - state.camY };
       e.preventDefault();
     } else if (e.button === 0 && !connectingRef.current) {
+      // On mobile (touch), single finger on empty canvas = pan
+      if (isMobile && e.pointerType === 'touch') {
+        state.panning = true;
+        state.panStart = { x: e.clientX - state.camX, y: e.clientY - state.camY };
+        e.preventDefault();
+        return;
+      }
       state.selectedModuleId = null;
       emit();
     }
-  }, []);
+  }, [isMobile]);
 
   const handlePointerMove = useCallback((e) => {
     if (state.panning && state.panStart) {