chore: bump version to 0.4.0, update changelog and all docs

Finalizes the 0.4.0 release:

- Version bumped to 0.4.0 in pyproject.toml
- CHANGELOG.md: add [0.4.0] section covering Frigate pre-upload scoring,
  quality replacement inversion, bootstrap fix, FRIGATE_SCORE_CEILING,
  ENABLE_FRIGATE_SCORES, removal of post-upload quality gate, and all
  doc/default corrections
- README.md: step 8 updated for dual-mode replacement, FRIGATE_SCORE_CEILING
  and ENABLE_FRIGATE_SCORES added to env var table, MIN_FACE_WIDTH and
  BLUR_THRESHOLD defaults corrected (50→90, 100→120)
- .env.example: FRIGATE_SCORE_THRESHOLD replaced with FRIGATE_SCORE_CEILING;
  QUALITY_REPLACEMENT line added; comments updated to match current semantics
- winnow/executor.py: bootstrap fix — recognize now called for all below-cap
  uploads when ENABLE_FRIGATE_SCORES=true (was gated on CEILING > 0)
- winnow/upload_tracker.py: frigate_scores schema comment corrected to
  pre-upload; get_most_redundant_mapped_file() added
- winnow/frigate_api.py: recognize_face returns (face_name, score)|None tuple
  so wrong-person scores never drive replacement or ceiling decisions
- winnow/config.py: FRIGATE_SCORE_THRESHOLD renamed to FRIGATE_SCORE_CEILING;
  ENABLE_FRIGATE_SCORES added
- tests/test_upload_tracker.py: 4 new tests for get_most_redundant_mapped_file

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

winnow/frigate_api.py

@@ -69,8 +69,13 @@ def get_frigate_person_files(person_name: str) -> list[str] | None:
     return files if isinstance(files, list) else []
 
 
-def recognize_face(file_path: str) -> float | None:
-    """Submit an image to Frigate's recognize endpoint and return the confidence score.
+def recognize_face(file_path: str) -> tuple[str | None, float] | None:
+    """Submit an image to Frigate's recognize endpoint.
+
+    Returns (face_name, score) where face_name is the best-matching person
+    (may be "unknown" if below Frigate's confidence threshold) and score is
+    the sigmoid-mapped cosine similarity (0-1) against that person's mean
+    embedding.
 
     Returns None if FRIGATE_URL is unset, the API is unreachable, no face is
     detected, or face recognition is not enabled in Frigate.
@@ -89,7 +94,7 @@ def recognize_face(file_path: str) -> float | None:
             return None
         data = resp.json()
         if data.get("success") and "score" in data:
-            return round(float(data["score"]), 4)
+            return (data.get("face_name"), round(float(data["score"]), 4))
         return None
     except Exception as e:
         logger.debug(f"Frigate recognize failed for {file_path}: {e}")