feat(i18n): the person page's biography in Hungarian, from TMDB's translation (E30 S4)

The /person fetch appends translations and keeps TMDB's Hungarian biography beside the instance-language
one (new plex_people.biography_hu, migration 0092). A Hungarian reader is served it, the English one when
TMDB has none. Already-enriched people are un-stamped, so their next open refetches them once.

backend/alembic/versions/0092_plex_person_biography_hu.py

@@ -0,0 +1,31 @@
+"""add biography_hu to plex_people — TMDB's Hungarian biography (E30 S4)
+
+Revision ID: 0092_plex_person_biography_hu
+Revises: 0091_plex_tagline_hu
+Create Date: 2026-09-29
+
+The person page showed a Hungarian reader the English biography although TMDB has a Hungarian one for
+most people. The person fetch now appends `translations` and keeps the Hungarian biography beside the
+English one. Already-enriched people are un-stamped, so their next page open refetches them once (the
+same lazy path as a first open) and fills it; until then the English biography stands in.
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0092_plex_person_biography_hu"
+down_revision: str | None = "0091_plex_tagline_hu"
+branch_labels: str | None = None
+depends_on: str | None = None
+
+
+def upgrade() -> None:
+    op.add_column("plex_people", sa.Column("biography_hu", sa.Text(), nullable=True))
+    op.execute(
+        "UPDATE plex_people SET tmdb_enriched_at = NULL "
+        "WHERE tmdb_person_id IS NOT NULL AND tmdb_enriched_at IS NOT NULL"
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("plex_people", "biography_hu")