refactor: optimize button animations and interval checks for performance

This commit introduces several performance improvements across the UI components:

- Updated the Button component to enhance hover animations by grouping styles for better GPU efficiency.
- Adjusted the interval timing in the BoardView and WorktreePanel components from 1 second to 3 and 5 seconds respectively, reducing CPU/GPU usage.
- Replaced the continuous gradient rotation animation with a subtle pulse effect in global CSS to further optimize rendering performance.

These changes aim to improve the overall responsiveness and efficiency of the UI components.

apps/ui/src/components/views/board-view.tsx

@@ -728,7 +728,7 @@ export function BoardView() {
 
     // Check immediately, then every 3 seconds
     checkAndStartFeatures();
-    const interval = setInterval(checkAndStartFeatures, 1000);
+    const interval = setInterval(checkAndStartFeatures, 3000);
 
     return () => {
       // Mark as inactive to prevent any pending async operations from continuing

apps/ui/src/components/views/board-view/worktree-panel/worktree-panel.tsx

@@ -102,12 +102,13 @@ export function WorktreePanel({
 
   const toggleCollapsed = () => setIsCollapsed((prev) => !prev);
 
-  // Periodic interval check (1 second) to detect branch changes on disk
+  // Periodic interval check (5 seconds) to detect branch changes on disk
+  // Reduced from 1s to 5s to minimize GPU/CPU usage from frequent re-renders
   const intervalRef = useRef<NodeJS.Timeout | null>(null);
   useEffect(() => {
     intervalRef.current = setInterval(() => {
       fetchWorktrees({ silent: true });
-    }, 1000);
+    }, 5000);
 
     return () => {
       if (intervalRef.current) {