fix duckdb filename, add db file and gitignore cleanup

- Dockerfile + start.sh: use basedosdados.duckdb (not basedosdados3.duckdb)
- add basedosdados.duckdb (3.5 MB, needed for Docker build)
- add requirements.txt (local dev use)
- .gitignore: remove *.duckdb exclusion, add .DS_Store

.gitignore

@@ -1,6 +1,5 @@
 .env
+.DS_Store
 logs/
-*.duckdb
-*.duckdb.wal
 done_tables.txt
 done_transfers.txt