feat: export music db in flatten format

.gitignore

@@ -8,6 +8,7 @@
 /players*.parquet
 /region*.parquet
 /records*.parquet
+/musics.parquet
 
 /.python-version
 /uv.lock

utils/export_musicdb_flat.py

@@ -0,0 +1,5 @@
+import polars as pl
+
+pl.read_json("music_db/src/musicDB.json").explode(pl.col("levels")).unnest(
+    pl.col("levels")
+).write_parquet("musics.parquet")