Change nginx site monitoring from HEAD to GET requests

- Fix false negatives for sites that don't handle HEAD requests properly
- Resolves photos.cmtec.se showing error when it actually works fine
- Improves compatibility with modern web applications

agent/src/collectors/service.rs

@@ -852,8 +852,8 @@ impl ServiceCollector {
         
         let start = Instant::now();
         
-        // Make HEAD request to avoid downloading content
-        match client.head(&url).send().await {
+        // Make GET request for better app compatibility (some apps don't handle HEAD properly)
+        match client.get(&url).send().await {
             Ok(response) => {
                 let latency = start.elapsed().as_millis() as f32;
                 let is_healthy = response.status().is_success() || response.status().is_redirection();