Wiki Phase 4: full-text search + revision history

Final phase of the wiki upgrade (see WIKI_UPGRADE.md).

Schema (additive): wiki_revisions table (per-save content snapshots).
The FULLTEXT index on wiki_pages(title, body) shipped in Phase 1.

Search:
- MATCH ... AGAINST natural-language search over title + body, ordered by
  relevance
- public: GET /public/wiki?q= (published only); admin: GET /admin/wiki?q=
  (all statuses)
- public wiki index gains a search box; admin list gains a search field

Revision history:
- every create/update snapshots the page into wiki_revisions
- admin endpoints: list revisions, get one, and restore (restore overwrites
  the page, rebuilds links, and appends a new revision — history stays
  append-only); logged as wiki.revision.restore
- editor gains a History modal: revision list + word-level diff (jsdiff) of a
  chosen revision against the current page, with one-click restore

Verified end-to-end: search matches body and title; two edits produce three
revisions; diff renders added/removed words; restore reverts and records a new
revision. No console errors.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

website/WIKI_UPGRADE.md

@@ -321,11 +321,16 @@ phase if preferred). Do not merge a phase that hasn't been verified.
 - Implementation note: links are plain anchors to `/wiki/<slug>` (the WYSIWYG fits
   this better than `[[ ]]` syntax); the sanitizer also allows `data-wiki-slug`.
 
-### Phase 4 — Discovery & trust
+### Phase 4 — Discovery & trust ✅
 - FULLTEXT search (public search box + admin filter); revision history list /
   diff / restore.
 - **Exit check**: search returns expected pages; edit a page twice, diff the
   revisions, restore an older one, confirm a new revision is recorded.
+- **Verified** (2026-06-27): `?q=` natural-language search matches on both body
+  (`recipes`→crafting) and title (`monsters`); the public search box and admin
+  filter both work. A page edited twice produced 3 revisions; the History modal
+  shows a word-level diff (added vs removed) of an old revision against current;
+  restoring reverted the page and appended a "Restored from revision #N" entry.
 
 ### Verification (every phase)
 Use the preview workflow, not manual hand-off: start the dev server, exercise the