Fix four quality-replacement bugs found by code re-audit

C1/C4: Cap blur-score computation at 1440 px before calling assess_quality
so scores are always on the same Laplacian scale as the embedding path
(which operates on Immich preview thumbnails). Also converts the image to
RGB before scoring and stores 0.0 on assess_quality failure so files
uploaded without a score remain eligible for future quality replacement
instead of occupying a slot permanently.

C2: Fall back to the tracker's mapped-filename set as the pre-upload
baseline when the Frigate GET /api/faces endpoint is unreachable at upload
start. Previously, uploads that succeeded during a partial API outage were
never mapped in frigate_files, leaving get_tracked_frigate_file_count
permanently under-counting those files and allowing Frigate to exceed
MAX_AUTO_IMAGES over time.

C3: Track min_quality_score_for_slot when a quality-replacement delete
succeeds but the subsequent upload fails. This ensures the freed slot can
only be filled by a candidate that beats the deleted file's score, not just
the next file in iteration order (which could be lower quality than what
was deleted).

Add get_tracked_frigate_filenames() to upload_tracker and expand tracker
tests to cover the new function and exclude-parameter behaviour.

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

tests/test_upload_tracker.py

@@ -156,3 +156,65 @@ def test_get_lowest_quality_mapped_file_skips_unscored():
     result = get_lowest_quality_mapped_file("Alice")
     assert result is not None
     assert result[1] == "asset-scored"  # only scored file is a candidate
+
+
+# ── get_tracked_frigate_filenames ─────────────────────────────────────────────
+
+def test_get_tracked_frigate_filenames_empty():
+    from winnow.upload_tracker import get_tracked_frigate_filenames
+    assert get_tracked_frigate_filenames("Alice") == set()
+
+
+def test_get_tracked_frigate_filenames_returns_mapped():
+    from winnow.upload_tracker import get_tracked_frigate_filenames, record_frigate_file
+    record_frigate_file("Alice", "Alice-1000.webp", "asset-a")
+    record_frigate_file("Alice", "Alice-1001.webp", "asset-b")
+    assert get_tracked_frigate_filenames("Alice") == {"Alice-1000.webp", "Alice-1001.webp"}
+
+
+def test_get_tracked_frigate_filenames_excludes_removed():
+    from winnow.upload_tracker import (
+        get_tracked_frigate_filenames,
+        record_frigate_file,
+        remove_frigate_file,
+    )
+    record_frigate_file("Alice", "Alice-1000.webp", "asset-a")
+    record_frigate_file("Alice", "Alice-1001.webp", "asset-b")
+    remove_frigate_file("Alice", "Alice-1000.webp")
+    assert get_tracked_frigate_filenames("Alice") == {"Alice-1001.webp"}
+
+
+def test_get_tracked_frigate_filenames_isolated_by_person():
+    from winnow.upload_tracker import get_tracked_frigate_filenames, record_frigate_file
+    record_frigate_file("Alice", "Alice-1000.webp", "asset-a")
+    record_frigate_file("Bob", "Bob-2000.webp", "asset-b")
+    assert get_tracked_frigate_filenames("Alice") == {"Alice-1000.webp"}
+    assert get_tracked_frigate_filenames("Bob") == {"Bob-2000.webp"}
+
+
+# ── get_lowest_quality_mapped_file with exclude ───────────────────────────────
+
+def test_get_lowest_quality_exclude_skips_specified_file():
+    from winnow.upload_tracker import (
+        get_lowest_quality_mapped_file,
+        mark_uploaded,
+        record_frigate_file,
+    )
+    mark_uploaded("asset-lo", person_name="Alice", score=0.10)
+    mark_uploaded("asset-hi", person_name="Alice", score=0.90)
+    record_frigate_file("Alice", "Alice-lo.webp", "asset-lo")
+    record_frigate_file("Alice", "Alice-hi.webp", "asset-hi")
+    result = get_lowest_quality_mapped_file("Alice", exclude={"Alice-lo.webp"})
+    assert result is not None
+    assert result[1] == "asset-hi"  # lo was excluded; hi is returned
+
+
+def test_get_lowest_quality_exclude_all_returns_none():
+    from winnow.upload_tracker import (
+        get_lowest_quality_mapped_file,
+        mark_uploaded,
+        record_frigate_file,
+    )
+    mark_uploaded("asset-a", person_name="Alice", score=0.50)
+    record_frigate_file("Alice", "Alice-a.webp", "asset-a")
+    assert get_lowest_quality_mapped_file("Alice", exclude={"Alice-a.webp"}) is None