Fix SvelteKit csrf deprecation and unused CSS warnings

Created by: jedmund

Summary

• Replace deprecated csrf.checkOrigin with trustedOrigins: [] in svelte.config.js
• Fix unused CSS warnings in tiptap/edra components by wrapping dynamically-injected selectors in :global()
• Remove dead CSS (.bubble-menu-button.active, .delete:hover, .animate-spin)

Test plan

• Verify build no longer warns about csrf.checkOrigin deprecation
• Verify unused CSS warnings are eliminated for UrlEmbedExtended, LinkEditDialog, ComposerBubbleMenu, Math, and MathInline
• Verify editor embed and bubble menu styling still works correctly