chore(tests): gate RLS tests behind RUN_RLS_TESTS flag

Continues the test-isolation work from dab740d. RLS migration tests run
against a policy-installed database and fail in the default create_all
suite, so they need to be opt-in:

- pytest.ini: register `rls` marker.
- conftest.py: auto-deselect test_rls_isolation.py unless
  RUN_RLS_TESTS=1. Drops the deprecated session-scoped event_loop
  fixture (not needed since pytest-asyncio 0.23+).
- test_rls_isolation.py: tag module with `rls` marker. Replace
  hardcoded `patherly_test` DB reference with parsed DATABASE_TEST_URL
  (matches conftest.py default `resolutionflow_test`). Updated docstring
  command to show RUN_RLS_TESTS=1.
- requirements-dev.txt: bump pytest-asyncio 0.23.0 → 0.24.0 (loop-scope
  marker behavior required by the RLS module fixture).

Run the RLS suite with:
  RUN_RLS_TESTS=1 DB_APP_ROLE_PASSWORD=... pytest tests/test_rls_isolation.py

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/conftest.py

@@ -4,8 +4,8 @@ Pytest configuration and fixtures for integration tests.
 Provides test database setup, client fixtures, and authentication helpers.
 """
 
-import asyncio
-from typing import AsyncGenerator, Generator
+import os
+from typing import AsyncGenerator
 import pytest
 import sqlalchemy as sa
 from httpx import AsyncClient, ASGITransport
@@ -26,7 +26,6 @@ settings.REQUIRE_INVITE_CODE = False
 # would silently nuke the dev database. Only DATABASE_TEST_URL is honored,
 # and the safety assertion below refuses to run against a DB whose name
 # doesn't contain "test".
-import os
 TEST_DATABASE_URL = os.environ.get(
     "DATABASE_TEST_URL",
     "postgresql+asyncpg://postgres:postgres@localhost:5432/resolutionflow_test",
@@ -43,13 +42,27 @@ assert "test" in _test_db_name, (
     f"test database (e.g. resolutionflow_test)."
 )
 
+_RUN_RLS_TESTS = os.environ.get("RUN_RLS_TESTS") == "1"
+_RLS_ISOLATION_FILE = "test_rls_isolation.py"
 
-@pytest.fixture(scope="session")
-def event_loop() -> Generator:
-    """Create an instance of the default event loop for each test case."""
-    loop = asyncio.get_event_loop_policy().new_event_loop()
-    yield loop
-    loop.close()
+
+def pytest_collection_modifyitems(config, items):
+    """Keep migration-managed RLS checks out of the default create_all suite."""
+    if _RUN_RLS_TESTS:
+        return
+
+    selected = []
+    deselected = []
+    for item in items:
+        item_path = getattr(item, "path", None) or getattr(item, "fspath", None)
+        if item_path and str(item_path).endswith(_RLS_ISOLATION_FILE):
+            deselected.append(item)
+        else:
+            selected.append(item)
+
+    if deselected:
+        config.hook.pytest_deselected(items=deselected)
+        items[:] = selected
 
 
 @pytest.fixture