fix(plex): summaries and taglines are stored as plain text

A Plex agent can hand a summary over as HTML (<p> paragraphs, &aacute;
entities); the info page and the hover card showed the tags. One cleaner,
app/plex/plaintext.py, now runs on every summary and tagline the sync, the
Hungarian overlay and the rich-detail fetch store, and migration 0101 cleans
the rows written before through the same function. Paragraph breaks survive
as newlines, which the info page and the hover card now keep.

backend/app/plex/overlay.py

@@ -17,6 +17,7 @@ from app.models import PlexItem, PlexLibrary, PlexShow
 from app.plex import sync as plex_sync
 from app.plex.client import PlexClient
 from app.plex.genres import hu_genres
+from app.plex.plaintext import plain_text
 
 log = logs.get_logger(__name__)
 
@@ -109,8 +110,8 @@ def _overlay_pass(
     for g, meta in hu_by_guid.items():
         targets = by_guid[g]
         title_hu = (meta.get("title") or "").strip() or None
-        summary_hu = meta.get("summary")
-        tagline_hu = (meta.get("tagline") or "").strip() or None
+        summary_hu = plain_text(meta.get("summary"))
+        tagline_hu = plain_text(meta.get("tagline"))
         genres_hu = hu_genres(plex_sync._tags(meta, "Genre"))
         for row in targets:
             row.title_hu = title_hu