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/model/wiki/wiki.db.js

@@ -63,6 +63,17 @@ async function findPublishedBySlug(slug) {
   return rows[0] || null
 }
 
+// Full-text search over title + body, ordered by relevance.
+async function searchSummaries(q, { publishedOnly = true } = {}) {
+  const pub = publishedOnly ? 'AND p.published = 1' : ''
+  return query(
+    `SELECT ${SUMMARY_COLS} ${FROM}
+     WHERE MATCH(p.title, p.body) AGAINST (? IN NATURAL LANGUAGE MODE) ${pub}
+     ORDER BY MATCH(p.title, p.body) AGAINST (?) DESC, p.title ASC`,
+    [q, q],
+  )
+}
+
 // ── Page writes ────────────────────────────────────────────────────────
 async function insert({
   slug,
@@ -233,6 +244,29 @@ async function getExistingSlugs(slugs) {
   return new Set(rows.map((r) => r.slug))
 }
 
+// ── Revisions ──────────────────────────────────────────────────────────
+async function insertRevision({ pageId, title, body, excerpt, categoryId, editorId, changeNote }) {
+  return query(
+    'INSERT INTO wiki_revisions (page_id, title, body, excerpt, category_id, editor_id, change_note) ' +
+      'VALUES (?, ?, ?, ?, ?, ?, ?)',
+    [pageId, title, body || null, excerpt || null, categoryId ?? null, editorId ?? null, changeNote || null],
+  )
+}
+
+async function listRevisions(pageId) {
+  return query(
+    `SELECT r.id, r.change_note, r.created_at, r.editor_id, u.username AS editor
+     FROM wiki_revisions r LEFT JOIN users u ON u.id = r.editor_id
+     WHERE r.page_id = ? ORDER BY r.id DESC`,
+    [pageId],
+  )
+}
+
+async function findRevision(id) {
+  const rows = await query('SELECT * FROM wiki_revisions WHERE id = ? LIMIT 1', [id])
+  return rows[0] || null
+}
+
 // ── Seeding (idempotent) ───────────────────────────────────────────────
 async function seedDefault(slug, title, body) {
   await query('INSERT IGNORE INTO wiki_pages (slug, title, body) VALUES (?, ?, ?)', [
@@ -264,6 +298,7 @@ module.exports = {
   listAllSummaries,
   findBySlug,
   findPublishedBySlug,
+  searchSummaries,
   insert,
   updateBySlug,
   deleteBySlug,
@@ -283,6 +318,9 @@ module.exports = {
   insertLink,
   getBacklinks,
   getExistingSlugs,
+  insertRevision,
+  listRevisions,
+  findRevision,
   seedDefault,
   seedDefaultCategory,
   assignCategoryBySlug,