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>

build/crontab

@@ -1 +1 @@
-0 6,18 * * * cd /app && bash /app/run_all.sh >> /proc/1/fd/1 2>> /proc/1/fd/2
+0 6,18 * * * cd /app && bash /app/run_all.sh --data-dir /app/data >> /proc/1/fd/1 2>> /proc/1/fd/2