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>

client/src/routes/admin/views/WikiEditor.jsx

@@ -1,5 +1,6 @@
 import { lazy, Suspense, useEffect, useState } from 'react'
 import Modal from '../../../components/Modal.jsx'
+import WikiHistory from './WikiHistory.jsx'
 import { api } from '../../../api/client.js'
 
 // Admin-only and heavy (TipTap) — load as its own chunk so the public bundle
@@ -22,6 +23,7 @@ export default function WikiEditor({ slug, onClose, onSaved }) {
   const [loading, setLoading] = useState(isEdit)
   const [busy, setBusy] = useState(false)
   const [error, setError] = useState('')
+  const [showHistory, setShowHistory] = useState(false)
 
   // Categories (dropdown) + pages (internal-link picker), for both new and edit.
   useEffect(() => {
@@ -110,6 +112,7 @@ export default function WikiEditor({ slug, onClose, onSaved }) {
   }
 
   return (
+    <>
     <Modal
       title={isEdit ? 'Edit wiki page' : 'New wiki page'}
       onClose={onClose}
@@ -121,6 +124,11 @@ export default function WikiEditor({ slug, onClose, onSaved }) {
               Delete
             </button>
           )}
+          {isEdit && (
+            <button onClick={() => setShowHistory(true)} disabled={busy} className="pill">
+              History
+            </button>
+          )}
           <button onClick={onClose} disabled={busy} className="pill">
             Cancel
           </button>
@@ -208,6 +216,17 @@ export default function WikiEditor({ slug, onClose, onSaved }) {
         </div>
       )}
     </Modal>
+    {showHistory && (
+      <WikiHistory
+        slug={slug}
+        onClose={() => setShowHistory(false)}
+        onRestored={() => {
+          setShowHistory(false)
+          onSaved()
+        }}
+      />
+    )}
+    </>
   )
 }