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>

server/src/router/v1/public/public.controller.js

@@ -68,6 +68,10 @@ async function getWikiTags(req, res) {
 
 async function getWikiList(req, res) {
   try {
+    // Full-text search takes precedence over category/tag filters.
+    const q = (req.query.q || '').trim()
+    if (q) return res.json(await wiki.search(q, { publishedOnly: true }))
+
     const filters = {}
     if (req.query.category) {
       const category = await wiki.getCategoryBySlug(req.query.category)