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/components/workspace/TabContent.tsx

@@ -4,6 +4,7 @@ import { TableDataView } from "@/components/table-viewer/TableDataView";
 import { TableStructure } from "@/components/table-viewer/TableStructure";
 import { RoleManagerView } from "@/components/management/RoleManagerView";
 import { SessionsView } from "@/components/management/SessionsView";
+import { EntityLookupPanel } from "@/components/lookup/EntityLookupPanel";
 
 export function TabContent() {
   const { tabs, activeTabId, updateTab } = useAppStore();
@@ -59,6 +60,13 @@ export function TabContent() {
           connectionId={activeTab.connectionId}
         />
       );
+    case "lookup":
+      return (
+        <EntityLookupPanel
+          key={activeTab.id}
+          connectionId={activeTab.connectionId}
+        />
+      );
     default:
       return null;
   }