dynamic port for UI from 8080 up (8081 etc) (#3042)

# Description of Changes

Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

src/main/java/stirling/software/SPDF/SPDFApplication.java

@@ -1,7 +1,6 @@
 package stirling.software.SPDF;
 
 import java.io.IOException;
-import java.net.ServerSocket;
 import java.net.URISyntaxException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -29,6 +28,7 @@ import stirling.software.SPDF.UI.WebBrowser;
 import stirling.software.SPDF.config.ConfigInitializer;
 import stirling.software.SPDF.config.InstallationPathConfig;
 import stirling.software.SPDF.model.ApplicationProperties;
+import stirling.software.SPDF.utils.UrlUtils;
 
 @Slf4j
 @EnableScheduling
@@ -64,6 +64,12 @@ public class SPDFApplication {
             app.setHeadless(false);
             props.put("java.awt.headless", "false");
             props.put("spring.main.web-application-type", "servlet");
+
+            int desiredPort = 8080;
+            String port = UrlUtils.findAvailablePort(desiredPort);
+            props.put("server.port", port);
+            System.setProperty("server.port", port);
+            log.info("Desktop UI mode: Using port {}", port);
         }
 
         app.setAdditionalProfiles(getActiveProfile(args));
@@ -160,7 +166,17 @@ public class SPDFApplication {
     }
 
     @Value("${server.port:8080}")
-    public void setServerPortStatic(String port) {
+    public void setServerPort(String port) {
+        if ("auto".equalsIgnoreCase(port)) {
+            // Use Spring Boot's automatic port assignment (server.port=0)
+            SPDFApplication.serverPortStatic =
+                    "0"; // This will let Spring Boot assign an available port
+        } else {
+            SPDFApplication.serverPortStatic = port;
+        }
+    }
+
+    public static void setServerPortStatic(String port) {
         if ("auto".equalsIgnoreCase(port)) {
             // Use Spring Boot's automatic port assignment (server.port=0)
             SPDFApplication.serverPortStatic =
@@ -197,36 +213,11 @@ public class SPDFApplication {
         return new String[] {"default"};
     }
 
-    private static boolean isPortAvailable(int port) {
-        try (ServerSocket socket = new ServerSocket(port)) {
-            return true;
-        } catch (IOException e) {
-            return false;
-        }
-    }
-
-    // Optionally keep this method if you want to provide a manual port-incrementation fallback.
-    private static String findAvailablePort(int startPort) {
-        int port = startPort;
-        while (!isPortAvailable(port)) {
-            port++;
-        }
-        return String.valueOf(port);
-    }
-
     public static String getStaticBaseUrl() {
         return baseUrlStatic;
     }
 
-    public String getNonStaticBaseUrl() {
-        return baseUrlStatic;
-    }
-
     public static String getStaticPort() {
         return serverPortStatic;
     }
-
-    public String getNonStaticPort() {
-        return serverPortStatic;
-    }
 }