Fix backend issues in desktop app (#4995)

# Description of Changes
Fixes two distinct but related issues in the backend of the desktop app:
- Correctly shows tools as unavaialable when the backend doesn't have
the dependencies or has disabled them etc. (same as web version - this
primarily didn't work on desktop because the app spawns before the
backend is running)
- Fixes infinite re-rendering issues caused by the app polling whether
the backend is healthy or not

app/core/src/main/java/stirling/software/SPDF/config/ExternalAppDepConfig.java

@@ -25,6 +25,7 @@ public class ExternalAppDepConfig {
     private final String weasyprintPath;
     private final String unoconvPath;
     private final Map<String, List<String>> commandToGroupMapping;
+    private volatile boolean dependenciesChecked = false;
 
     public ExternalAppDepConfig(
             EndpointConfiguration endpointConfiguration, RuntimePathConfig runtimePathConfig) {
@@ -111,6 +112,10 @@ public class ExternalAppDepConfig {
         }
     }
 
+    public boolean isDependenciesChecked() {
+        return dependenciesChecked;
+    }
+
     @PostConstruct
     public void checkDependencies() {
         // Check core dependencies
@@ -162,5 +167,7 @@ public class ExternalAppDepConfig {
             }
         }
         endpointConfiguration.logDisabledEndpointsSummary();
+        dependenciesChecked = true;
+        log.info("Dependency checks completed");
     }
 }

app/core/src/main/java/stirling/software/SPDF/controller/api/misc/ConfigController.java

@@ -35,6 +35,7 @@ public class ConfigController {
     private final EndpointConfiguration endpointConfiguration;
     private final ServerCertificateServiceInterface serverCertificateService;
     private final UserServiceInterface userService;
+    private final stirling.software.SPDF.config.ExternalAppDepConfig externalAppDepConfig;
 
     public ConfigController(
             ApplicationProperties applicationProperties,
@@ -43,12 +44,14 @@ public class ConfigController {
             @org.springframework.beans.factory.annotation.Autowired(required = false)
                     ServerCertificateServiceInterface serverCertificateService,
             @org.springframework.beans.factory.annotation.Autowired(required = false)
-                    UserServiceInterface userService) {
+                    UserServiceInterface userService,
+            stirling.software.SPDF.config.ExternalAppDepConfig externalAppDepConfig) {
         this.applicationProperties = applicationProperties;
         this.applicationContext = applicationContext;
         this.endpointConfiguration = endpointConfiguration;
         this.serverCertificateService = serverCertificateService;
         this.userService = userService;
+        this.externalAppDepConfig = externalAppDepConfig;
     }
 
     @GetMapping("/app-config")
@@ -56,6 +59,9 @@ public class ConfigController {
         Map<String, Object> configData = new HashMap<>();
 
         try {
+            // Add dependency check status
+            configData.put("dependenciesReady", externalAppDepConfig.isDependenciesChecked());
+
             // Get AppConfig bean
             AppConfig appConfig = applicationContext.getBean(AppConfig.class);