Unify hover behavior across all sidebar selectors

- Update view-selector-dropdown hover to match theme/style selectors
- Change from var(--glass-bg-light) to rgba(255, 255, 255, 0.15)
- Ensures consistent glassmorphism hover effects throughout sidebar
- Provides cohesive user experience across Week/Month, Theme, and Style dropdowns

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/styles.css

@@ -1639,7 +1639,7 @@ body {
 }
 
 .view-selector-dropdown:hover {
-    background: var(--glass-bg-light);
+    background: rgba(255, 255, 255, 0.15);
     border-color: var(--glass-bg-lighter);
 }