feat: confidence scores, Frigate-authoritative capacity cap

- Store Immich face confidence scores per asset in frigate_uploaded_ids.json
- Add frigate_api.py: query GET /api/faces to count trained images per person
- Record Frigate training count as frigate_count in tracker for offline fallback
- MAX_AUTO_IMAGES cap now uses live Frigate count → cached frigate_count → local uploaded count
- Startup summary shows last known Frigate training count per person
- Migrate by_person entries from flat list to {asset_ids, scores, frigate_count} dict

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

winnow/frigate_api.py

@@ -0,0 +1,28 @@
+"""Frigate API helpers for querying face training state."""
+
+import logging
+import os
+
+import requests
+
+logger = logging.getLogger(__name__)
+
+
+def get_frigate_face_counts() -> dict[str, int] | None:
+    """Return {person_name: training_image_count} from Frigate's train directory.
+
+    Returns None if FRIGATE_URL is not set or the API is unreachable, so callers
+    can distinguish "API unavailable" from "person has 0 images."
+    """
+    frigate_url = os.environ.get("FRIGATE_URL", "").rstrip("/")
+    if not frigate_url:
+        return None
+    try:
+        resp = requests.get(f"{frigate_url}/api/faces", timeout=10)
+        resp.raise_for_status()
+        data = resp.json()
+        train = data.get("train", {})
+        return {name: len(files) for name, files in train.items() if isinstance(files, list)}
+    except Exception as e:
+        logger.warning(f"Could not query Frigate face counts: {e}")
+        return None