Add runtime filter, kid-friendly toggle, surprise me, and re-roll

- Runtime quick-select buttons (Any/90m/2h/2.5h) filter movies by length
- Kid-friendly toggle forces PG-13 max and boosts Family/Animation genres
- Surprise Me picks a random mood prompt from 20 curated options
- Show Me More re-rolls same mood excluding already-shown movies
- Re-roll appends new results to the existing search history entry

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

app/services/prefilter.py

@@ -98,7 +98,7 @@ def _parse_movie(raw: dict) -> Movie:
     )
 
 
-def prefilter_candidates(movies_raw: list[dict], mood: str, max_candidates: int = 200) -> list[Movie]:
+def prefilter_candidates(movies_raw: list[dict], mood: str, max_candidates: int = 200, kid_friendly: bool = False) -> list[Movie]:
     """Score and filter movies based on mood signals. Returns top candidates as Movie models."""
     mood_lower = mood.lower()
 
@@ -108,6 +108,12 @@ def prefilter_candidates(movies_raw: list[dict], mood: str, max_candidates: int
     max_rating: str | None = None
     decade = _parse_decade(mood)
 
+    # Kid-friendly toggle overrides
+    if kid_friendly:
+        max_rating = "PG-13"
+        boost_genres.update(["Family", "Animation", "Comedy", "Adventure"])
+        penalize_genres.update(["Horror", "Thriller"])
+
     for keyword, signals in MOOD_SIGNALS.items():
         if keyword in mood_lower:
             boost_genres.update(signals["boost"])