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/wiki/Wiki.jsx

@@ -1,3 +1,4 @@
+import { useState } from 'react'
 import { Link, useSearchParams } from 'react-router-dom'
 import PublicLayout from '../../components/PublicLayout.jsx'
 import PageHeader from '../../components/PageHeader.jsx'
@@ -5,6 +6,30 @@ import { Loading, ErrorState, EmptyState } from '../../components/PageState.jsx'
 import { useAsync } from '../../lib/useAsync.js'
 import { api } from '../../api/client.js'
 
+function SearchBox({ initial, onSubmit }) {
+  const [term, setTerm] = useState(initial || '')
+  return (
+    <form
+      onSubmit={(e) => {
+        e.preventDefault()
+        onSubmit(term.trim())
+      }}
+      style={{ display: 'flex', gap: 8, maxWidth: 460, margin: '0 auto 8px' }}
+    >
+      <input
+        type="search"
+        value={term}
+        onChange={(e) => setTerm(e.target.value)}
+        className="input"
+        placeholder="Search the wiki…"
+      />
+      <button type="submit" className="btn btn-primary btn-sq">
+        Search
+      </button>
+    </form>
+  )
+}
+
 // Group published pages under their category, preserving category sort order and
 // collecting anything uncategorized into a trailing section.
 function groupByCategory(categories, pages) {
@@ -36,16 +61,19 @@ function PageCard({ page }) {
 }
 
 export default function Wiki() {
-  const [searchParams] = useSearchParams()
+  const [searchParams, setSearchParams] = useSearchParams()
   const activeCategory = searchParams.get('category')
   const activeTag = searchParams.get('tag')
-  // Tag view fetches a tag-filtered page list; otherwise all pages (grouped here).
+  const activeQ = searchParams.get('q')
+  // Search / tag views fetch a filtered page list; otherwise all pages (grouped here).
+  const pageOpts = activeQ ? { q: activeQ } : activeTag ? { tag: activeTag } : {}
   const { loading, error, data } = useAsync(
     () =>
-      Promise.all([api.wikiCategories(), api.wiki(activeTag ? { tag: activeTag } : {})]).then(
-        ([categories, pages]) => ({ categories, pages }),
-      ),
-    [activeTag],
+      Promise.all([api.wikiCategories(), api.wiki(pageOpts)]).then(([categories, pages]) => ({
+        categories,
+        pages,
+      })),
+    [activeTag, activeQ],
   )
 
   const allSections = data ? groupByCategory(data.categories, data.pages) : []
@@ -53,7 +81,10 @@ export default function Wiki() {
     ? allSections.filter((s) => s.slug === activeCategory)
     : allSections
   const hasPages = data && data.pages.length > 0
-  const filtered = Boolean(activeCategory || activeTag)
+  const flat = Boolean(activeTag || activeQ) // flat-list views
+  const filtered = Boolean(activeCategory || activeTag || activeQ)
+
+  const runSearch = (term) => setSearchParams(term ? { q: term } : {})
 
   return (
     <PublicLayout section="wiki">
@@ -64,6 +95,8 @@ export default function Wiki() {
           title="Mysticmoon Wiki"
           lead="A calm starting point for shard guides, the world and its lore, gameplay systems, and community rules."
         />
+        <SearchBox initial={activeQ || ''} onSubmit={runSearch} />
+
         {loading && <Loading />}
         {error && <ErrorState message="Could not load the wiki right now." />}
         {!loading && !error && !hasPages && !filtered && <EmptyState>No wiki pages yet.</EmptyState>}
@@ -74,13 +107,14 @@ export default function Wiki() {
               ← All sections
             </Link>
             {activeTag && <span className="muted"> · Tagged #{activeTag}</span>}
+            {activeQ && <span className="muted"> · Results for “{activeQ}”</span>}
           </p>
         )}
 
-        {/* Tag view: a flat list of matching pages (tags cross categories). */}
-        {!loading && !error && activeTag &&
+        {/* Flat list: search results or a tag filter (both cross categories). */}
+        {!loading && !error && flat &&
           (data.pages.length === 0 ? (
-            <EmptyState>No pages with this tag.</EmptyState>
+            <EmptyState>{activeQ ? 'No pages match that search.' : 'No pages with this tag.'}</EmptyState>
           ) : (
             <div className="grid-4" style={{ marginTop: 12 }}>
               {data.pages.map((p) => (
@@ -90,10 +124,10 @@ export default function Wiki() {
           ))}
 
         {/* Category / full view: grouped sections. */}
-        {!loading && !error && !activeTag && hasPages && activeCategory && sections.length === 0 && (
+        {!loading && !error && !flat && hasPages && activeCategory && sections.length === 0 && (
           <EmptyState>No pages in this section yet.</EmptyState>
         )}
-        {!activeTag &&
+        {!flat &&
           sections.map((section) => (
             <section key={section.id} style={{ marginTop: 36 }}>
               <h2