fix: all site-scoped links use siteUrlBase in hub mode
Follow-up on the feed fix (612b102). The same class of bug was still present in:
- post.ejs: tag, edit, delete links + comment forms + comment delete
+ login-next -> now with siteUrlBase prefix
- bottom-tab.ejs: "Write" FAB (/posts/new)
- home.ejs: empty-state "Write your first post"
- profile-sheet.ejs: "New post"
- search.ejs: search form action
Without the prefix these fell back to the primary site in hub (404 /
wrong site). In solo siteUrlBase is empty -> behavior unchanged.
Co-Authored-By: Claude <noreply@…>