fix: Multiple ADHD/Focus Tools fixes

Switch/Checkbox Styling:
- Exclude switches and checkboxes from larger-targets CSS
- Fix checkbox square aspect ratio when ADHD mode enabled
- Prevent padding from being applied to form controls

Quick Wins Count:
- Use settings.quickWinThreshold instead of hardcoded 15
- Match same filtering logic as QuickWinList component

Back Button Navigation:
- Use window.history.back() instead of setLocation('/')
- Works correctly when navigating from ADHD dashboard to sub-pages

Time Tracking (Break Reminder):
- Track only active browser time using Page Visibility API
- Reset accumulated time after 8 hours of inactivity
- Store/restore active time in localStorage properly
- No more 1500+ hour counts from leaving browser open

Sources:
- https://ui.shadcn.com/docs/theming (shadcn theming)
- https://ui.shadcn.com/docs/tailwind-v4 (Tailwind v4 updates)

client/src/pages/BodyDoublingPage.tsx

@@ -28,7 +28,7 @@ export default function BodyDoublingPage() {
         <Button
           variant="ghost"
           size="icon"
-          onClick={() => setLocation('/')}
+          onClick={() => window.history.back()}
           className="shrink-0"
         >
           <ArrowLeft className="h-5 w-5" />