fix(plex,audit): E30 review round 1 — the people job keeps going, HU genres everywhere, results as data

- people_enrich: a failed TMDB lookup or a dead headshot is skipped, not the end of the run (a dead
  file is marked and left for a week; three failures in a row end it); portraits wait for the Plex
  module switch; a no-Plex original keeps its own cache key, so the resize still replaces it; the job
  entry lives in the plex domain (run_people_enrich)
- person-image takes only a headshot-shaped CDN url (no query variants of one file)
- every synced row gets Hungarian genres, and a HU genre filter matches the word as picked too;
  migration 0094 fills the rows no overlay reached
- a job run's audit row carries its result as data; audit_clear / demo_reset store their counts
- one credit-column list for the prune and the enrichment order; _overlay_pass typed
- tests: batch skip + stop, HU bio stored, dead headshots, module switch, the person-image route,
  the job body, genre filter + facet write + twin fallback, tagline/summary fallbacks, audit data,
  the reader's alphabet at every remaining collated() call site

backend/app/plex/imgcache.py

@@ -8,6 +8,9 @@ few hundred MB at most for a big library — acceptable, matching the download d
 The cache directory (``cache.CACHE_DIR``) is shared with the subtitle cache (see ``subtitles.py``).
 """
 
+import time
+from datetime import timedelta
+
 from fastapi import Response
 from sqlalchemy.orm import Session
 
@@ -78,6 +81,27 @@ def drop(key: str) -> None:
             pass
 
 
+def mark_miss(key: str) -> None:
+    """Remember that `key`'s source could not be fetched (an empty `.miss` file; its mtime is when), so
+    a prefetch can leave a dead source alone for a while. Best-effort."""
+    try:
+        CACHE_DIR.mkdir(parents=True, exist_ok=True)
+        (CACHE_DIR / f"{key}.miss").touch()
+    # silent-ok: without the mark the dead source is only asked for again on the next run.
+    except OSError:
+        pass
+
+
+def missed_within(key: str, age: timedelta) -> bool:
+    """`key` was marked as a miss less than `age` ago."""
+    try:
+        mtime = (CACHE_DIR / f"{key}.miss").stat().st_mtime
+    # silent-ok: no mark (the usual case).
+    except OSError:
+        return False
+    return time.time() - mtime < age.total_seconds()
+
+
 def write(key: str, data: bytes, ct: str) -> None:
     ext = _CT_EXT.get((ct or "").split(";")[0].strip(), "jpg")
     try: