feat: add cross-database entity lookup for searching column values across all databases

Enables searching for a specific column value (e.g. carrier_id=123) across all databases on a PostgreSQL server. The backend creates temporary connection pools per database (semaphore-limited to 5), queries information_schema for matching columns, and executes read-only SELECTs with real-time progress events. Results are grouped by database/table in a new "Entity Lookup" tab.

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

src-tauri/src/lib.rs

@@ -88,6 +88,13 @@ pub fn run() {
             commands::saved_queries::list_saved_queries,
             commands::saved_queries::save_query,
             commands::saved_queries::delete_saved_query,
+            // ai
+            commands::ai::get_ai_settings,
+            commands::ai::save_ai_settings,
+            commands::ai::list_ollama_models,
+            commands::ai::generate_sql,
+            // lookup
+            commands::lookup::entity_lookup,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");