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>