Replace custom logging with tracing crate and RUST_LOG env var

- Remove custom logging module and init_logging function
- Update main.rs to use tracing_subscriber with EnvFilter
- Remove log_level from global config structure
- Update documentation and tests to use RUST_LOG
- Format long lines in config.rs and test files for better readability

tests/rate_limiting.rs

@@ -13,7 +13,8 @@ fn test_rate_limiting_with_concurrent_requests() {
     let cert_path = temp_dir.path().join("cert.pem");
     let key_path = temp_dir.path().join("key.pem");
 
-    let config_content = format!(r#"
+    let config_content = format!(
+        r#"
 bind_host = "127.0.0.1"
 port = {}
 max_concurrent_requests = 1
@@ -22,7 +23,12 @@ max_concurrent_requests = 1
 root = "{}"
 cert = "{}"
 key = "{}"
-    "#, port, root_dir.display(), cert_path.display(), key_path.display());
+    "#,
+        port,
+        root_dir.display(),
+        cert_path.display(),
+        key_path.display()
+    );
     std::fs::write(&config_path, config_content).unwrap();
 
     // Start server binary with test delay to simulate processing time
@@ -30,7 +36,7 @@ key = "{}"
         .arg("--config")
         .arg(&config_path)
         .arg("--test-processing-delay")
-        .arg("3")  // 3 second delay per request
+        .arg("3") // 3 second delay per request
         .spawn()
         .expect("Failed to start server");
 
@@ -68,13 +74,30 @@ key = "{}"
     let rate_limited_count = results.iter().filter(|r| r.starts_with("41")).count();
 
     // Debug output
-    println!("Results: {:?}", results);
-    println!("Success: {}, Rate limited: {}", success_count, rate_limited_count);
+    tracing::debug!("Test results: {:?}", results);
+    tracing::debug!(
+        "Success: {}, Rate limited: {}",
+        success_count,
+        rate_limited_count
+    );
 
     // Strict validation - rate limiting must work deterministically with delay
-    assert_eq!(success_count, 1, "Expected exactly 1 successful request with limit=1, got {}. Results: {:?}", success_count, results);
-    assert_eq!(rate_limited_count, 4, "Expected exactly 4 rate limited requests with limit=1, got {}. Results: {:?}", rate_limited_count, results);
+    assert_eq!(
+        success_count, 1,
+        "Expected exactly 1 successful request with limit=1, got {}. Results: {:?}",
+        success_count, results
+    );
+    assert_eq!(
+        rate_limited_count, 4,
+        "Expected exactly 4 rate limited requests with limit=1, got {}. Results: {:?}",
+        rate_limited_count, results
+    );
 
     // Verify all requests received valid responses
-    assert_eq!(success_count + rate_limited_count, 5, "All 5 requests should receive responses. Results: {:?}", results);
-}
+    assert_eq!(
+        success_count + rate_limited_count,
+        5,
+        "All 5 requests should receive responses. Results: {:?}",
+        results
+    );
+}