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/elements/element_tiptap_editor.scss

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