Horizons improvements: UI refinements, file uploads, and publishing fixes

This week's Horizons updates include: the restore/undo button has moved to the bottom of messages for better UX; you can now upload .ico files; image upload errors are now clear and informational, checking file count, type, and size in order; the "Create new website" button in the top menu is always active and opens projects in a new tab instead of blocking during generation; website publishing no longer waits for sitemap generation to complete, eliminating timeout failures; and you'll now see which messages have deducted credits and which haven't, making billing clearer.