Wiki Phase 1: categories, drafts/publish, HTML sanitization

Foundation & safety phase of the wiki upgrade (see WIKI_UPGRADE.md).

Schema (additive, idempotent via ensureSchema):
- new wiki_categories table; wiki_pages gains category_id, excerpt,
  published, published_at, sort_order, and a FULLTEXT index
- migration ALTERs guarded with IF NOT EXISTS for existing databases
- seed reworked into 4 sections with the 8 starter pages assigned

Security:
- new utils/sanitizeHtml.js (sanitize-html allowlist); wiki bodies are
  sanitized on every save, and the article renders through DOMPurify
- strips <script>, event handlers (onerror), and javascript: URLs

Backend:
- public: published-only list with ?category filter + /wiki/categories
- admin: extended page CRUD, PATCH publish toggle, category CRUD;
  drafts visible to admin, hidden from public
- all writes logged to activity_log

Frontend:
- data-driven public wiki index (sections + real descriptions; removed
  hardcoded blurbs/Roman numerals) with ?category filtering
- article: category breadcrumb + sanitized render
- admin: Section/Status columns, draft/publish + section + excerpt in the
  editor, and a Manage sections modal

Verified end-to-end against MariaDB 11: migration clean, XSS neutralized,
drafts hidden, client builds, server boots.

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

website/WIKI_UPGRADE.md

@@ -284,7 +284,7 @@ phase if preferred). Do not merge a phase that hasn't been verified.
 ### Phase 0 — Branch & scaffolding ✅ (this doc)
 - `wiki-upgrade` branch created; this spec committed.
 
-### Phase 1 — Foundation & safety (highest value)
+### Phase 1 — Foundation & safety (highest value) ✅
 - Schema: add `wiki_categories`, alter `wiki_pages` (category_id, excerpt, published,
   published_at, sort_order, FULLTEXT), update `seed.js`.
 - Server: server-side sanitization on save; drafts/publish endpoints; categories CRUD;
@@ -293,6 +293,11 @@ phase if preferred). Do not merge a phase that hasn't been verified.
   `WikiArticle.jsx`; draft/publish + category in the (still-textarea) admin editor.
 - **Exit check**: existing pages still render; XSS payload in body is neutralized;
   draft pages hidden from the public list/article.
+- **Verified** (2026-06-27): schema migration ran clean on MariaDB 11; XSS payload
+  (`<script>`, `onerror=`, `javascript:`) stripped server-side; drafts return 404 on
+  the public API and are absent from the public list while visible in admin; public
+  index is data-driven (categories + sections); article shows category breadcrumb;
+  client builds and server boots with no errors.
 
 ### Phase 2 — Authoring UX
 - TipTap editor replaces the textarea; generalized `/admin/uploads`; inline images.