feat: improve test reliability and add request tracing

- Add retry configuration for flaky tests (2 retries for default, 3 for
OAuth)
- Configure test groups with proper concurrency limits (serial: 1,
integration: 4)
- Add tower-http tracing layer with custom span formatting for HTTP
requests
- Simplify database pool handling by removing unnecessary Arc wrapper
- Improve test context setup with better logging and error handling
- Refactor user creation parameters for better clarity and consistency
- Add debug logging for OAuth cookie handling

Cargo.lock

@@ -3130,6 +3130,7 @@ dependencies = [
  "testcontainers",
  "time",
  "tokio 1.47.1",
+ "tower-http",
  "tracing",
  "tracing-futures",
  "tracing-subscriber",
@@ -5474,6 +5475,7 @@ dependencies = [
  "tower",
  "tower-layer",
  "tower-service",
+ "tracing",
 ]
 
 [[package]]