Add --data-dir CLI argument to replace symlink-based data persistence

The Docker entrypoint previously created symlinks from /app/ to /app/data/
so that scripts writing relative paths would persist to the mounted volume.
This caused symlink loops in production when stale symlinks leaked into the
host data directory.

Instead, all scrapers, merge_and_map.py, regen_map.py, and run_all.sh now
accept a --data-dir argument (default: ".") that controls where data files
are read from and written to. The entrypoint and crontab pass
--data-dir /app/data, eliminating the need for symlinks entirely.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

regen_map.py

@@ -5,6 +5,7 @@ Doplní chybějící plochy ze Sreality API, opraví URL, aplikuje filtry.
 """
 from __future__ import annotations
 
+import argparse
 import json
 import time
 import urllib.request
@@ -57,8 +58,9 @@ def fetch_area(hash_id: int) -> int | None:
     return None
 
 
-def main():
-    json_path = Path("byty_sreality.json")
+def main(data_dir: str = "."):
+    data_path = Path(data_dir)
+    json_path = data_path / "byty_sreality.json"
     if not json_path.exists():
         print("Soubor byty_sreality.json nenalezen. Nejprve spusť scrape_and_map.py")
         return
@@ -100,15 +102,19 @@ def main():
     print(f"Zbývá: {len(filtered)} bytů")
 
     # Save updated data
-    filtered_path = Path("byty_sreality.json")
+    filtered_path = data_path / "byty_sreality.json"
     filtered_path.write_text(
         json.dumps(filtered, ensure_ascii=False, indent=2),
         encoding="utf-8",
     )
 
     # Generate map
-    generate_map(filtered)
+    generate_map(filtered, output_path=str(data_path / "mapa_bytu.html"))
 
 
 if __name__ == "__main__":
-    main()
+    parser = argparse.ArgumentParser(description="Regenerate map from existing data")
+    parser.add_argument("--data-dir", type=str, default=".",
+                        help="Directory for reading/writing data files (default: current dir)")
+    args = parser.parse_args()
+    main(data_dir=args.data_dir)