refactor: address Svelte compiler warnings and improve a11y/security

- Convert decorative labels to spans to fix a11y warnings in Accounts and Sites pages
- Add rel="noopener noreferrer" to external links for security
- Use untrack for Svelte 5 state initialization from props in e_app_sign_in_out.svelte
- Make TipTap editor styles global to fix scoping warnings for dynamic content

src/lib/ae_core/ae_comp__site_config_editor.svelte

@@ -117,7 +117,7 @@
                     <div class="flex gap-2">
                         <input type="text" bind:value={cfg_json.header_image_path} class="input variant-form-material grow" placeholder="https://..." />
                         {#if cfg_json.header_image_path}
-                            <a href={cfg_json.header_image_path} target="_blank" class="btn-icon variant-soft-surface"><ExternalLink size="1.2em" /></a>
+                            <a href={cfg_json.header_image_path} target="_blank" rel="noopener noreferrer" class="btn-icon variant-soft-surface"><ExternalLink size="1.2em" /></a>
                         {/if}
                     </div>
                 </label>

src/lib/app_components/e_app_sign_in_out.svelte

@@ -37,10 +37,10 @@
 
     let { log_lvl = $bindable(0), data = null, hidden = $bindable(true) }: Props = $props();
 
-    let url_user_id = $state(data?.url?.searchParams?.get('user_id'));
-    let url_user_key = $state(data?.url?.searchParams?.get('user_key')); // Reminder that "key" is the site's auth key.
-    let url_user_username = $state(data?.url?.searchParams?.get('username'));
-    let url_user_email = $state(data?.url?.searchParams?.get('user_email'));
+    let url_user_id = $state(untrack(() => data?.url?.searchParams?.get('user_id')));
+    let url_user_key = $state(untrack(() => data?.url?.searchParams?.get('user_key'))); // Reminder that "key" is the site's auth key.
+    let url_user_username = $state(untrack(() => data?.url?.searchParams?.get('username')));
+    let url_user_email = $state(untrack(() => data?.url?.searchParams?.get('user_email')));
 
     $effect(() => {
         // NOTE: Sync URL params to state. 

src/lib/elements/element_tiptap_editor.scss

@@ -1,5 +1,5 @@
 /* Basic editor styles */
-.tiptap {
+:global(.tiptap) {
     :first-child {
         margin-top: 0;
     }