Fixes three critical bugs:
1. Fixed inactivity popup appearing on every rotated site
- userInteractedWithCurrentSite now resets when switching sites
- Each site independently tracks user interaction
- Popup only appears on sites user actually touched
2. Fixed rotation not resuming after "I'm still here" response
- Clicking "I'm still here" now sets manualNavigationMode=false
- Rotation resumes after user acknowledges prompt
3. Fixed rotation stuck after media playback ends
- After media grace period (30s), manualNavigationMode resets
- Prevents black screen when media stops
- Normal rotation automatically resumes
User-reported issue: Sites showing for full duration, no popup spam,
media playback properly returns to rotation.
