Cleanup UI buttons + smarter series-aware search title

UI: Hide developer tools (Cover-aus-Datei, Tags-lesen,
Connectivity-Check) behind a '+ Tools' toggle. Default view has only
Play, Match, Auto-Match. Tag extraction runs automatically on scan
anyway, so the buttons were noise.

Matcher: Item metadata (series, author from tags or earlier matches)
now flows into the search:
- detect_series() also scans inside title, not only prefix — handles
  garbage chars (◆ U+25C6 etc.) before the series name
- New _strip_series_prefix removes "Die drei ???" from search title so
  APIs see only the episode title ("Die Villa der Toten") which is how
  most databases index these
- _build_search_title also strips non-printable / exotic chars and
  bracketed content anywhere (not just trailing)
- Effective series falls back to item.series when detect_series misses
- Search call now logs which series the search is using

Example: title='◆Die◆ drei ??? Die Villa der Toten (drei Fragezeichen)'
  detected_series='Die drei ???', search_title='Die Villa der Toten'

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/routers/matching.py

@@ -119,12 +119,16 @@ async def debug_match(
     from ..services.matching.open_library import search_open_library
     from ..services.matching.google_books import search_google_books
     from ..services.matching.dnb import search_dnb
-    from ..services.matcher import _build_search_title, detect_series
+    from ..services.matcher import _build_search_title, detect_series, _strip_series_prefix
 
     series, episode = detect_series(title)
-    search_title = _build_search_title(title)
     if series and episode:
         search_title = f"{series} {episode}"
+    elif series:
+        cleaned = _build_search_title(title)
+        search_title = _strip_series_prefix(cleaned, series)
+    else:
+        search_title = _build_search_title(title)
 
     logger.info(f"DEBUG: title={title!r} → search={search_title!r} series={series!r} episode={episode!r}")