refactor(logging): move logging setup to internal/logging

Moves logging configuration and setup to a dedicated package. Updates Config struct to use nested LoggingConfig. Updates main.go to use the new logging package.

config/config.yaml

@@ -1,7 +1,12 @@
 # Application Configuration
 # This file contains the default configuration for the application.
 # Values can be overridden by environment variables with the prefix "APP_".
-# Example: APP_LOG_LEVEL=debug
+# Example: APP_LOGGING_LEVEL=debug
 
-# Log Level: debug, info, warn, error
-log_level: "info"
+logging:
+  # Log Level: debug, info, warn, error
+  level: "info"
+
+server:
+  host: "localhost"
+  port: 8080