feat(config): enforce minimum qpdf version requirement (#4907)

# Description of Changes


- Added validation to ensure qpdf version is at least 12.0.0
- Disabled corresponding groups if the installed version is below the
requirement
- Logged warnings for unsupported or undetermined versions
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- Why the change was made
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---

## Checklist

### General

- [X] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [X] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/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/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [X] I have performed a self-review of my own code
- [X] 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/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### 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/devGuide/DeveloperGuide.md#6-testing)
for more details.

Signed-off-by: Balázs Szücs <bszucs1209@gmail.com>

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

@@ -148,6 +148,31 @@ public class ExternalAppDepConfig {
                                     "WeasyPrint version could not be determined ({} --version)",
                                     command));
         }
+
+        // Extra: enforce minimum qpdf version if command matches
+        if (isQpdf(command)) {
+            Optional<String> version = getVersionSafe(command, "--version");
+            version.ifPresentOrElse(
+                    v -> {
+                        Version installed = new Version(v);
+                        Version required = new Version("12.0.0");
+                        if (installed.compareTo(required) < 0) {
+                            List<String> affectedGroups =
+                                    commandToGroupMapping.getOrDefault(command, List.of("qpdf"));
+                            for (String group : affectedGroups) {
+                                endpointConfiguration.disableGroup(group);
+                            }
+                            log.warn(
+                                    "qpdf version {} is below required {} - disabling group(s): {}",
+                                    installed,
+                                    required,
+                                    String.join(", ", affectedGroups));
+                        } else {
+                            log.info("qpdf {} meets minimum {}", installed, required);
+                        }
+                    },
+                    () -> log.warn("qpdf version could not be determined ({} --version)", command));
+        }
     }
 
     private boolean isWeasyprint(String command) {
@@ -155,6 +180,10 @@ public class ExternalAppDepConfig {
                 || command.toLowerCase(Locale.ROOT).contains("weasyprint");
     }
 
+    private boolean isQpdf(String command) {
+        return command.toLowerCase(Locale.ROOT).contains("qpdf");
+    }
+
     private List<String> getAffectedFeatures(String group) {
         List<String> endpoints = new ArrayList<>(endpointConfiguration.getEndpointsForGroup(group));
         return endpoints.stream().map(this::formatEndpointAsFeature).toList();