test(backend): add comprehensive tests for OAuth and agent endpoints

- Added tests for OAuth provider admin and consent endpoints covering edge cases.
- Extended agent-related tests to handle incorrect project associations and lifecycle state transitions.
- Introduced tests for sprint status transitions and validation checks.
- Improved multiline formatting consistency across all test functions.

backend/tests/models/syndarix/test_project.py

@@ -100,7 +100,9 @@ class TestProjectModel:
         db_session.add(project)
         db_session.commit()
 
-        retrieved = db_session.query(Project).filter_by(slug="timestamp-project").first()
+        retrieved = (
+            db_session.query(Project).filter_by(slug="timestamp-project").first()
+        )
 
         assert isinstance(retrieved.created_at, datetime)
         assert isinstance(retrieved.updated_at, datetime)
@@ -177,7 +179,11 @@ class TestProjectEnums:
             db_session.add(project)
             db_session.commit()
 
-            retrieved = db_session.query(Project).filter_by(slug=f"project-{level.value}").first()
+            retrieved = (
+                db_session.query(Project)
+                .filter_by(slug=f"project-{level.value}")
+                .first()
+            )
             assert retrieved.autonomy_level == level
 
     def test_all_project_statuses(self, db_session):
@@ -192,7 +198,11 @@ class TestProjectEnums:
             db_session.add(project)
             db_session.commit()
 
-            retrieved = db_session.query(Project).filter_by(slug=f"project-status-{status.value}").first()
+            retrieved = (
+                db_session.query(Project)
+                .filter_by(slug=f"project-status-{status.value}")
+                .first()
+            )
             assert retrieved.status == status
 
 
@@ -227,7 +237,10 @@ class TestProjectSettings:
 
         assert retrieved.settings == complex_settings
         assert retrieved.settings["mcp_servers"] == ["gitea", "slack", "file-system"]
-        assert retrieved.settings["webhook_urls"]["on_issue_created"] == "https://example.com/issue"
+        assert (
+            retrieved.settings["webhook_urls"]["on_issue_created"]
+            == "https://example.com/issue"
+        )
         assert "important" in retrieved.settings["tags"]
 
     def test_empty_settings(self, db_session):