fix: invalidate stale page analysis when a re-crawl overwrites a page

Deterministic per-page storage keys mean a re-crawl overwrites the image but the
pages row survives the upsert, so analysis keyed to page_id (page_analysis/
search_doc, OCR, auto-tags, content-warnings) stayed stale forever and
force=false re-enqueue never re-analyzed it — poisoning search + the derived
manga_content_warnings (audit DB-1). persist_pages now detects conflict-updated
pages via xmax and clears their four derived tables in the same tx (the
content-warnings DELETE fires the mcw_* triggers), returning them to unanalyzed
so they re-derive. Tested.

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

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.128.11",
+  "version": "0.128.12",
   "private": true,
   "type": "module",
   "scripts": {