Add comprehensive documentation and unit tests

Documentation:
- Add detailed README files for all services (auth, character, database, launcher, packet, utils, world)
- Create API documentation for the database service with detailed endpoint specifications
- Document database schema and relationships
- Add service architecture overviews and configuration instructions

Unit Tests:
- Implement comprehensive test suite for database repositories (user, character, session)
- Add gRPC service tests for database interactions
- Create tests for packet service components (bufferpool, connection, packets)
- Add utility service tests (health check, logging, load balancer, redis cache, service discovery)
- Implement auth service user tests
- Add character service tests

Code Structure:
- Reorganize test files into a more consistent structure
- Create a dedicated tests crate for integration testing
- Add test helpers and mock implementations for easier testing

tests/utils/logging_tests.rs

@@ -0,0 +1,42 @@
+use std::env;
+use utils::logging::setup_logging;
+
+#[test]
+fn test_logging_setup() {
+    // Test with default log level
+    env::remove_var("LOG_LEVEL");
+    setup_logging("test_app", &["test_crate"]);
+    
+    // Test with custom log level
+    env::set_var("LOG_LEVEL", "debug");
+    setup_logging("test_app", &["test_crate"]);
+    
+    // Test with invalid log level (should default to info)
+    env::set_var("LOG_LEVEL", "invalid_level");
+    setup_logging("test_app", &["test_crate"]);
+    
+    // Test with multiple additional crates
+    setup_logging("test_app", &["test_crate1", "test_crate2", "test_crate3"]);
+    
+    // Clean up
+    env::remove_var("LOG_LEVEL");
+}
+
+#[test]
+fn test_logging_output() {
+    // This test is more of a smoke test to ensure logging doesn't panic
+    // Actual log output verification would require capturing stdout/stderr
+    
+    env::set_var("LOG_LEVEL", "trace");
+    setup_logging("test_logging", &[]);
+    
+    // Log at different levels
+    tracing::error!("This is an error message");
+    tracing::warn!("This is a warning message");
+    tracing::info!("This is an info message");
+    tracing::debug!("This is a debug message");
+    tracing::trace!("This is a trace message");
+    
+    // Clean up
+    env::remove_var("LOG_LEVEL");
+}