A01: Per-source health affects community_scheduler overall status

Bug: community_scheduler always had status='ready' even when individual
sources were failed or stale. Success of one source masked failure of another.

Fix:
- Overall status is 'degraded' if any enabled source has failed
- Overall status is 'stale' if all sources are stale but none failed
- Overall status is 'ready' only when at least one source is healthy
- Overall status is 'not_started' when no sources are enabled
- Readiness (ready flag) still NOT blocked by import health (A01 requirement)

Verification:
- 7/7 readiness tests pass
- 121/121 Python tests pass (1 skipped)
- Failed/stale sources are now visible in JSON without blocking scheduler

apps/api/tests/test_readiness.py

@@ -122,8 +122,8 @@ def test_community_scheduler_stale_does_not_block_readiness() -> None:
             session, AvailableStorage(), import_required=False,
             import_interval_seconds=3600, community_import_interval_seconds=1800, now=now,
         )
-    assert ready is True  # A01: stale does NOT block
-    assert components["community_scheduler"]["status"] == "ready"
+    assert ready is True  # A01: stale does NOT block readiness
+    assert components["community_scheduler"]["status"] == "stale"  # Overall reflects stale source
     assert components["community_scheduler"]["sources"]["rf4db"]["status"] == "stale"
     assert components["community_scheduler"]["sources"]["rf4db"]["blocking"] is False
 
@@ -148,8 +148,8 @@ def test_community_scheduler_failed_does_not_block_readiness() -> None:
             session, AvailableStorage(), import_required=False,
             import_interval_seconds=3600, community_import_interval_seconds=1800, now=now,
         )
-    assert ready is True  # A01: failed does NOT block
-    assert components["community_scheduler"]["status"] == "ready"
+    assert ready is True  # A01: failed does NOT block readiness
+    assert components["community_scheduler"]["status"] == "degraded"  # Overall reflects failed source
     assert components["community_scheduler"]["sources"]["rf4db"]["status"] == "failed"
     assert components["community_scheduler"]["sources"]["rf4db"]["blocking"] is False