Huddle pins, GitLab comment sync, and full-text search

• Huddle pin mode — data-mode="pin" places markers on a live site and opens feedback into your board.
• GitLab outbound — public comments on linked posts post notes back to the GitLab issue or MR.
• Lexical search — Postgres tsvector ranking for posts, docs, and changelog (semantic/pgvector still next).
• UX polish — / search hint, sticky changelog filters on mobile, docs TOC on large screens, kanban scroll fade.

Apply migrations 0097_git_comment_links and 0098_search_tsvector before relying on outbound sync or FTS in production.