feat: add column sort, SQL formatter, table stats, insert dialog, saved queries & sessions monitor

- Column sort by header click in table view (ASC/DESC/none cycle, server-side)
- SQL formatter with Format button and Shift+Alt+F keybinding (sql-formatter)
- Table size and row count display in schema tree via pg_class
- Insert row dialog with column type hints and auto-skip for identity columns
- Saved queries (bookmarks) with CRUD backend, sidebar panel, and save dialog
- Active sessions monitor (pg_stat_activity) with auto-refresh, cancel & terminate

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/commands/mod.rs

@@ -4,4 +4,5 @@ pub mod export;
 pub mod history;
 pub mod management;
 pub mod queries;
+pub mod saved_queries;
 pub mod schema;