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

dev/convert_video_for_rpi.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+# Video Conversion Script for Raspberry Pi Signage Player
+# Converts videos to optimal settings: 1080p @ 30fps, H.264 codec
+
+if [ $# -eq 0 ]; then
+    echo "Usage: $0 <input_video> [output_video]"
+    echo "Example: $0 input.mp4 output.mp4"
+    echo ""
+    echo "This script converts videos to Raspberry Pi-friendly settings:"
+    echo "  - Resolution: Max 1920x1080"
+    echo "  - Frame rate: 30 fps"
+    echo "  - Codec: H.264"
+    echo "  - Bitrate: ~5-8 Mbps"
+    exit 1
+fi
+
+INPUT_VIDEO="$1"
+OUTPUT_VIDEO="${2:-converted_$(basename "$INPUT_VIDEO")}"
+
+if [ ! -f "$INPUT_VIDEO" ]; then
+    echo "Error: Input file '$INPUT_VIDEO' not found!"
+    exit 1
+fi
+
+echo "Converting video for Raspberry Pi playback..."
+echo "Input:  $INPUT_VIDEO"
+echo "Output: $OUTPUT_VIDEO"
+echo ""
+
+# Convert video with optimal settings for Raspberry Pi
+ffmpeg -i "$INPUT_VIDEO" \
+    -c:v libx264 \
+    -preset medium \
+    -crf 23 \
+    -maxrate 8M \
+    -bufsize 12M \
+    -vf "scale='min(1920,iw)':'min(1080,ih)':force_original_aspect_ratio=decrease,fps=30" \
+    -r 30 \
+    -c:a aac \
+    -b:a 128k \
+    -movflags +faststart \
+    -y \
+    "$OUTPUT_VIDEO"
+
+if [ $? -eq 0 ]; then
+    echo ""
+    echo "✓ Conversion completed successfully!"
+    echo "Original: $(du -h "$INPUT_VIDEO" | cut -f1)"
+    echo "Converted: $(du -h "$OUTPUT_VIDEO" | cut -f1)"
+    echo ""
+    echo "You can now use '$OUTPUT_VIDEO' in your signage player."
+else
+    echo ""
+    echo "✗ Conversion failed! Make sure ffmpeg is installed:"
+    echo "  sudo apt-get install ffmpeg"
+    exit 1
+fi