Cap quality replacement against tracked files only, not total Frigate count

Previously, effective_count and the jobs.py cap check used the total
Frigate file count (including manually-added files), so any file a user
curated by hand ate into winnow's managed quota. Now:

- get_tracked_frigate_file_count() returns len(frigate_files) from the
  tracker — only files winnow uploaded and reconciled
- effective_count in the upload loop uses this tracker count so
  manually-added files are invisible to the cap
- jobs.py capacity check uses len(frigate_files) instead of the live
  Frigate API count or cached frigate_count
- Frigate API call for known_frigate_files_at_start is now only used
  for the post-upload reconciliation diff, not for cap enforcement

Side-effect: fixes audit bug #1 — an unreachable Frigate GET no longer
zeroes effective_count and bypasses the cap, because the cap is now
read from the always-available local tracker.

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

tests/test_upload_tracker.py

@@ -102,6 +102,23 @@ def test_remove_frigate_file_does_not_unmark_asset():
     assert filter_already_uploaded(["asset-a1"]) == []
 
 
+def test_get_tracked_frigate_file_count_zero_when_empty():
+    from winnow.upload_tracker import get_tracked_frigate_file_count
+    assert get_tracked_frigate_file_count("Alice") == 0
+
+
+def test_get_tracked_frigate_file_count_counts_only_mapped():
+    """Only files explicitly recorded via record_frigate_file count toward the cap."""
+    from winnow.upload_tracker import get_tracked_frigate_file_count, mark_uploaded, record_frigate_file
+    mark_uploaded("asset-a", person_name="Alice")
+    mark_uploaded("asset-b", person_name="Alice")
+    record_frigate_file("Alice", "Alice-1000.webp", "asset-a")
+    # asset-b is uploaded but not yet mapped — does not count
+    assert get_tracked_frigate_file_count("Alice") == 1
+    record_frigate_file("Alice", "Alice-1001.webp", "asset-b")
+    assert get_tracked_frigate_file_count("Alice") == 2
+
+
 def test_get_lowest_quality_mapped_file_none_when_empty():
     from winnow.upload_tracker import get_lowest_quality_mapped_file
     assert get_lowest_quality_mapped_file("Alice") is None