Cleanup repo + harden offline install and watchdog

Repo hygiene:
- Remove dead scripts (.wait-for-display, .display-keepalive, .keep-screen-alive)
- Remove stale backup/scratch (install.sh.bak, New.txt, stale .pyc)
- Stop tracking machine-specific/generated state (config/app_config.json,
  playlists/server_playlist.json, src/player_auth.json, generated launchers)
- Prune duplicate wheel versions (one per package)
- Reorganize working_files -> dev/, dev/tests/, documentation/dev-notes/, scripts/
- Extend .gitignore; fix no-op rules in repo/.gitignore

Offline install (install.sh):
- Non-fatal system-dep step; per-package apt retry; .deb bundle install
- Skip pip self-upgrade offline; guard online fallbacks behind connectivity probe
- Dependency-free fetch_url (curl/wget/urllib); --no-reboot flag
- Fix corrupted literal backslash-bang escapes (shebangs, test -f, banner)
- Idempotent cron install (no more stacked @reboot lines)

Autostart / watchdog:
- start.sh: single-instance flock lock (.player_watchdog.lock) acquired only
  after a display is confirmed, preventing parallel watchdogs
- Set XDG_RUNTIME_DIR when missing; exit early if headless
- run_player.sh: activate .venv; stop_player.sh: clear lock file

.gitignore

@@ -30,24 +30,48 @@ env/
 *.pyc
 
 # Media files (optional - remove if you want to track media)
-media/*.jpg
-media/*.jpeg
-media/*.png
-media/*.gif
-media/*.bmp
-media/*.mp4
-media/*.avi
-media/*.mkv
-media/*.mov
-media/*.webm
+media/**/*.jpg
+media/**/*.jpeg
+media/**/*.png
+media/**/*.gif
+media/**/*.bmp
+media/**/*.mp4
+media/**/*.avi
+media/**/*.mkv
+media/**/*.mov
+media/**/*.webm
 
-# Playlists cache (auto-generated)
-playlists/server_playlist_*.json
+# Downloaded / on-device edited media (server-managed runtime content)
+media/edited_media/
+
+# Playlists cache (auto-generated by the player)
+playlists/server_playlist*.json
+
+# Player configuration (machine-specific; install.sh writes a template if absent)
+config/app_config.json
 
 # Logs
 *.log
 .kivy/
 
+# Runtime state (generated by the player / watchdog)
+.player_heartbeat
+.player_stop_requested
+.player_watchdog.lock
+.post-clone-setup.done
+.post-clone-backups/
+
+# Installer-generated launchers (recreated by install.sh)
+.run-background.sh
+.start-player-cron.sh
+
+# Secrets / machine-specific auth tokens (never commit)
+player_auth.json
+
+# Local backups / editor leftovers
+*.bak
+*~
+
 # IDE
 .vscode/
 .idea/