Security fixes, enterprise stuff and more (#3241)

# Description of Changes

Please provide a summary of the changes, including:

- Enable user to add custom JAVA ops with env JAVA_CUSTOM_OPTS
- Added support for prometheus (enabled via JAVA_CUSTOM_OPTS +
enterprise license)
- Changed settings from enterprise naming to 'Premium'
- KeygenLicense Check to support offline licenses
- Disable URL-to-PDF due to huge security bug
- Remove loud Split PDF logs
- addUsers renamed to adminSettings
- Added Usage analytics page
- Add user button to only be enabled based on total users free
- Improve Merge memory usage


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.

---------

Co-authored-by: a <a>
Co-authored-by: pixeebot[bot] <104101892+pixeebot[bot]@users.noreply.github.com>
Co-authored-by: Connor Yoh <[email protected]>

src/main/resources/templates/account.html

@@ -349,7 +349,7 @@
               </script>
               <div class="mb-3 mt-4 text-center">
                 <a th:href="@{'/logout'}" role="button" class="btn btn-danger" th:text="#{account.signOut}">Sign Out</a>
-                <a th:if="${role == 'ROLE_ADMIN'}" class="btn btn-info" th:href="@{'/addUsers'}" role="button" th:text="#{account.adminSettings}" target="_blank">Admin Settings</a>
+                <a th:if="${role == 'ROLE_ADMIN'}" class="btn btn-info" th:href="@{'/adminSettings'}" role="button" th:text="#{account.adminSettings}" target="_blank">Admin Settings</a>
               </div>
             </div>
           </div>