test(kevin): fix enum assertion + mark Postgres-dependent tests as integration

Pipeline #46 surfaced two pre-existing CI bugs once fakeredis was
installed and tests could collect:

1. test_models.py:389 asserted "DISCOVERED" in status_col.type.enums,
   but the model defines KevinVideoStatus with values_callable so
   .enums returns the lowercase string values, not member names.
   Asserting "discovered" instead.

2. Four test files use the db_session fixture which requires a real
   Postgres on localhost:5432. CI has no Postgres, so 10 tests failed
   with Connect call failed (errno 111). These genuinely need a DB —
   mirroring tests/integration/* which already use
   @pytest.mark.integration. Adding module-level
   pytestmark = pytest.mark.integration to:
   - tests/shared/models/test_meet_kevin_trading.py
   - tests/services/kevin_signal_bridge/test_aggregator.py
   - tests/services/kevin_signal_bridge/test_audit.py
   - tests/services/kevin_signal_bridge/test_exit_scanner.py

CI runs with -m "not integration" so they're now deselected.
Local pytest still picks them up by default (no marker filter).

tests/services/kevin_signal_bridge/test_aggregator.py

@@ -6,6 +6,8 @@ from decimal import Decimal
 import pytest
 from sqlalchemy.ext.asyncio import AsyncSession
 
+pytestmark = pytest.mark.integration
+
 from services.kevin_signal_bridge.aggregator import MentionAggregator
 from shared.models.meet_kevin import (
     KevinAnalysis,

tests/services/kevin_signal_bridge/test_audit.py

@@ -7,6 +7,8 @@ import pytest
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+pytestmark = pytest.mark.integration
+
 from services.kevin_signal_bridge.audit import AuditWriter
 from shared.models.meet_kevin import (
     KevinAnalysis,

tests/services/kevin_signal_bridge/test_exit_scanner.py

@@ -7,6 +7,8 @@ from unittest.mock import AsyncMock, MagicMock
 import pytest
 from sqlalchemy.ext.asyncio import AsyncSession
 
+pytestmark = pytest.mark.integration
+
 from services.kevin_signal_bridge.exit_scanner import ExitScanner
 from shared.constants.kevin import KEVIN_STRATEGY_UUID
 from shared.models.meet_kevin import (

tests/shared/models/test_meet_kevin_trading.py

@@ -8,6 +8,8 @@ import pytest
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+pytestmark = pytest.mark.integration
+
 from shared.models.meet_kevin import (
     KevinAnalysis,
     KevinChannel,

tests/test_models.py

@@ -383,10 +383,10 @@ class TestMeetKevinModels:
         assert KevinAnalysis.__tablename__ == "kevin_analyses"
         assert KevinStockMention.__tablename__ == "kevin_stock_mentions"
 
-        # Check that KevinVideo.status is an Enum containing "DISCOVERED"
+        # SAEnum uses values_callable, so .enums returns lowercase values, not member names.
         status_col = KevinVideo.__table__.c.status
         assert status_col is not None
-        assert "DISCOVERED" in status_col.type.enums
+        assert "discovered" in status_col.type.enums
 
         # Check relationships exist
         assert hasattr(KevinChannel, "videos")