feat: deployment support and production readiness

- Add deployment section to README (systemd, Docker, nginx reverse proxy)
- Add environment variable support to server.py (PORT, PGN_URL, CACHE_TTL)
- Update .gitignore for Python artifacts and lara-chess directory
- Improve board/navigation UX in app.js (userScrolledMoves tracking,
  updateClocks function, better game switching)

server.py

@@ -14,11 +14,11 @@ import time
 import json
 from datetime import datetime
 
-PGN_URL = "https://www.deutsche-schachjugend.de/2026/odjm-d/partien/gesamt-utf8.pgn"
-PORT = 8111
+PGN_URL = os.environ.get("PGN_URL", "https://www.deutsche-schachjugend.de/2026/odjm-d/partien/gesamt-utf8.pgn")
+PORT = int(os.environ.get("PORT", 8111))
 CACHE_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "cache")
 CACHE_FILE = os.path.join(CACHE_DIR, "gesamt-utf8.pgn")
-CACHE_TTL = 30  # Sekunden
+CACHE_TTL = int(os.environ.get("CACHE_TTL", 30))  # Sekunden
 
 os.makedirs(CACHE_DIR, exist_ok=True)