feat(search): frontend content search (text + warnings) + manga warning banner

Surfaces the analysis pipeline in the UI:

- api clients: searchPages() + PageSearchItem/ContentWarning types;
  listMangas cwInclude/cwExclude; MangaDetail.content_warnings.
- /search gains a content-search mode: free-text over OCR+scene and
  tri-state content-warning toggles (include/exclude), driven by URL
  params (text, cw_include, cw_exclude) and the new /me/page-search
  endpoint. Tag browsing is preserved when no content filter is active.
- manga detail renders a deduped content-warning banner.

Tests: vitest param serialization (searchPages CSV/text/cw, listMangas
cw); Playwright text-search + cw-toggle flows (route-mocked). svelte-check
+ build clean; full vitest (258) + search e2e (7) green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/Cargo.lock

@@ -1517,7 +1517,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mangalord"
-version = "0.70.0"
+version = "0.71.0"
 dependencies = [
  "anyhow",
  "argon2",