fix(12-uat): add display_name_override schema regression + Compose hardening

- test_list_connections_reads_display_name_override_column: proves GET /api/cloud/connections
  does not raise UndefinedColumn (direct Phase 12 UAT blocker regression)
- docker-compose: promtail socket :ro, Grafana password fail-fast (:?)
- test_migration_0006: DDL privilege test fails not skips when role absent
- README: version 0.2.1

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

backend/tests/test_cloud.py

@@ -310,6 +310,32 @@ async def test_webdav_connect_validates(async_client, db_session, monkeypatch):
     assert resp.status_code == 422
 
 
+async def test_list_connections_reads_display_name_override_column(
+    async_client, db_session, cloud_connection_factory
+):
+    """GET /api/cloud/connections must succeed after migration 0006.
+
+    Regression for Phase 12 UAT blocker: psycopg.errors.UndefinedColumn was raised
+    because cloud_connections.display_name_override did not exist in the live schema.
+    This test proves the ORM can read all Phase 12 columns without schema errors.
+    """
+    auth = await _create_user_and_token(db_session, role="user")
+    await cloud_connection_factory(db_session, auth["user"].id, provider="nextcloud")
+
+    resp = await async_client.get(
+        "/api/cloud/connections",
+        headers=auth["headers"],
+    )
+
+    assert resp.status_code == 200, f"Unexpected status: {resp.status_code} — {resp.text}"
+    data = resp.json()
+    assert isinstance(data.get("items"), list)
+    assert len(data["items"]) == 1
+    conn = data["items"][0]
+    assert conn["provider"] == "nextcloud"
+    assert "credentials_enc" not in conn
+
+
 # ── CLOUD-02: Credential encryption round-trip ────────────────────────────────
 
 async def test_credentials_enc_not_exposed(