Suppress maxminddb DEBUG logs in tracing filter

maxminddb's deserializer emits high-volume DEBUG traces for every field
decoded during a GeoIP lookup. Adding a target-specific directive
(maxminddb=warn) keeps those logs silent while leaving the rest of the
application at its configured level.

https://claude.ai/code/session_01Wen51749mAnwBEfh7XmvUw

net-guardia/src/utils/logging.rs

@@ -39,10 +39,14 @@ impl Logging {
             Level::INFO
         };
 
+        let env_filter = EnvFilter::from_default_env()
+            .add_directive(level.into())
+            .add_directive("maxminddb=warn".parse().expect("valid directive"));
+
         tracing_subscriber::registry()
             .with(stdout_layer)
             .with(file_layer)
-            .with(EnvFilter::from_default_env().add_directive(level.into()))
+            .with(env_filter)
             .init();
 
         Ok(())