style: add custom-scrollbar styling to all dialog scrollable areas

Added custom-scrollbar class to scrollable elements in:
- EffectBrowser dialog content area
- ProjectsDialog projects list
- CommandPalette results list
- Modal content area
- TrackList automation parameter label containers

This ensures consistent scrollbar styling across all dialogs and UI elements.

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

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

components/dialogs/ProjectsDialog.tsx

@@ -76,7 +76,7 @@ export function ProjectsDialog({
         </div>
 
         {/* Projects List */}
-        <div className="flex-1 overflow-y-auto p-6">
+        <div className="flex-1 overflow-y-auto custom-scrollbar p-6">
           {projects.length === 0 ? (
             <div className="flex flex-col items-center justify-center py-12 text-center">
               <FolderOpen className="h-16 w-16 text-muted-foreground mb-4" />