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

repo/.gitignore

@@ -1,6 +1,10 @@
-# Ignore downloaded packages but keep directory structure
-repo/python-wheels/*.whl
-repo/python-wheels/*.tar.gz
-repo/system-packages/debs/
-!repo/python-wheels/.gitkeep
-!repo/system-packages/.gitkeep
+# Patterns are relative to THIS file (the repo/ folder), so no "repo/" prefix.
+# (The previous patterns used a "repo/" prefix and therefore never matched.)
+
+# Downloaded system .deb bundles are large and optional.
+# Fetch on demand with:  bash scripts/download_deb_packages.sh
+# They are intentionally NOT committed.
+system-packages/debs/
+
+# NOTE: Python wheels under python-wheels/ ARE committed on purpose, so that a
+# plain `git clone` ships a complete offline install bundle.

repo/README.md

@@ -13,21 +13,23 @@ The installer script (`install.sh`) will automatically use this repo folder if a
 
 ### To populate this folder for offline installation:
 
-Run the download script from the project root:
+Run the download scripts from the project root:
 ```bash
-bash download_offline_packages.sh
+bash scripts/download_offline_packages.sh
+bash scripts/download_deb_packages.sh
 ```
 
-This will download all necessary Python wheels and document system packages.
+This will download all necessary Python wheels and system .deb packages.
 
 ## Contents
 
-### Python Packages
-- kivy==2.1.0
-- requests==2.32.4
+### Python Packages (see requirements.txt for the source of truth)
+- kivy==2.3.1
+- requests==2.34.2
 - bcrypt==4.2.1
-- aiohttp==3.9.1
-- asyncio==3.4.3
+- aiohttp==3.11.16
+- ffpyplayer==4.5.3
+- evdev==1.9.1
 - All dependencies
 
 ### System Packages (APT)