large query reduction (#5754)

# Description of Changes

Reduce endpoint-availability call so that an empty param to it returns
all endpoints to avoid pointlessly large http headers


Before:
GET
/api/v1/config/endpoints-availability?endpoints=compress-pdf%2Crotate-pdf%2Cmerge-pdfs%2Csplit-pages%2Cocr-pdf
  for all 74 tools

  After:
  GET /api/v1/config/endpoints-availability
---

## 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/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)
- [ ] 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/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.

app/common/src/main/java/stirling/software/SPDF/config/EndpointConfiguration.java

@@ -606,6 +606,12 @@ public class EndpointConfiguration {
         return endpointGroups.getOrDefault(group, new HashSet<>());
     }
 
+    public Set<String> getAllEndpoints() {
+        return endpointGroups.values().stream()
+                .flatMap(Set::stream)
+                .collect(java.util.stream.Collectors.toSet());
+    }
+
     private boolean isToolGroup(String group) {
         return "qpdf".equals(group)
                 || "OCRmyPDF".equals(group)