Add GET /people browse/discover endpoint

Extends the browse/discover pattern already built for movies/series
to the fourth major entity type. No genre/year/status equivalent for
people -- known_for_department is the one categorical filter that
actually means something for a cast/crew list, and sort_by is just
popularity (default) or name. No invalid-filter case either: unlike
genre/status, known_for_department is a plain string compared
directly, nothing to parse or validate.

build_person_summary refactored to share row-to-summary logic with
the new list path, same pattern used for movies/series/companies.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

app/schemas/person.py

@@ -70,3 +70,11 @@ class PersonCreditsOut(BaseModel):
     id: str
     cast: list[FilmographyCreditOut] = []
     crew: list[FilmographyCreditOut] = []
+
+
+class PersonListOut(BaseModel):
+    page: int
+    page_size: int
+    total_results: int
+    total_pages: int
+    results: list[PersonSummaryOut] = []