feat(sys-menu): add URL param builder to app config panel

New e_app_url_builder.svelte component lets admins construct and copy
shareable URLs with any combination of core global params (iframe, theme,
theme_mode, key). Outputs full URL by default; toggleable to params-only
string for pasting onto existing links. Integrated into e_app_cfg Utilities
section (visible in edit mode).

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

src/lib/app_components/e_app_cfg.svelte

@@ -3,6 +3,7 @@
 
     import { ae_util } from '$lib/ae_utils/ae_utils';
     import { ae_loc, ae_sess, ae_api, slct, slct_trigger } from '$lib/stores/ae_stores';
+    import E_app_url_builder from '$lib/app_components/e_app_url_builder.svelte';
 
     // import Element_theme from '$lib/e_app_theme.svelte';
 
@@ -230,6 +231,10 @@
             </div>
         </section>
         <!-- END: Utilities -->
+
+        <section class="space-y-2">
+            <E_app_url_builder />
+        </section>
     </div>
 
     <!-- class:justify-between={expand}