feat: implement saved queries feature with file list UI - Enrich Rust list_saved_queries to return file metadata - Add saved queries section in DatabaseBrowser with context menu - Auto-refresh list after save, switch to existing tab if file open - Connection-prefixed default filenames (lowercase, hyphen-separated) - Fix false unsaved indicator when switching tabs - Reorder nav: Connections → Queries → Import/Export → History - Hide Data Studio from navigation

feat: implement saved queries feature with file list UI - Enrich Rust list_saved_queries to return file metadata - Add saved queries section in DatabaseBrowser with context menu - Auto-refresh list after save, switch to existing tab if file open - Connection-prefixed default filenames (lowercase, hyphen-separated) - Fix false unsaved indicator when switching tabs - Reorder nav: Connections → Queries → Import/Export → History - Hide Data Studio from navigation #10