add export.py for proxy list export

CLI tool for exporting working proxies:
- multiple formats: txt, json, csv, length-prefixed
- filters: protocol, country, anonymity, max latency
- sorting: latency, added time, success count
- configurable output limit

Also update .gitignore to exclude data/ directory

.gitignore

@@ -6,5 +6,4 @@ __pycache__/
 *.sqlite-shm
 *.sqlite-wal
 .claude/
-data/*.BIN
-data/*.dat
+data/