Add asinfo package for AS number information lookups

- Created pkg/asinfo with embedded AS data from ipverse/asn-info
- Provides fast lookups by ASN with GetDescription() and GetHandle()
- Includes Search() functionality for finding AS by name/handle
- Added asinfo-gen tool to fetch and convert CSV data to JSON
- Added 'make asupdate' target to refresh AS data
- Embedded JSON data contains 130k+ AS entries
- Added comprehensive tests and examples

.gitignore

@@ -25,4 +25,7 @@ go.work.sum
 # Database files
 *.db
 *.db-journal
-*.db-wal
+*.db-wal
+
+# Temporary files
+*.tmp