feat: add URL deep-linking for DataGrids

- Add PageUrlState utility for URL ↔ state serialization
- Add column `id` field for unique column identification in URLs
- Update idSelector to return String for URL compatibility
- All DataGrid pages now support URL params: search, sort, order, id
- Browser URL updates via replaceState (no GoRouter rebuilds)
- Add FilterPanelSemantics for filter panel semantic IDs
- Add TESTING.md documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/features/security/router.dart

@@ -61,8 +61,11 @@ List<RouteBase> securityRoutes() {
       GoRoute(
         path: nav.path,
         name: 'security${_capitalize(nav.id.replaceAll('-', '_'))}',
-        pageBuilder: (context, state) =>
-            noTransitionPage(context, state, SecurityPage(nav: nav)),
+        pageBuilder: (context, state) => noTransitionPage(
+          context,
+          state,
+          SecurityPage(nav: nav, routerState: state),
+        ),
       ),
   ];
 }