refactor: move modules under app/ directory and update file paths (#3938)

# Description of Changes

- **What was changed:**  
- Renamed top-level directories: `stirling-pdf` → `app/core`, `common` →
`app/common`, `proprietary` → `app/proprietary`.
- Updated all path references in `.gitattributes`, GitHub workflows
(`.github/workflows/*`), scripts (`.github/scripts/*`), `.gitignore`,
Dockerfiles, license files, and template settings to reflect the new
structure.
- Added a new CI job `check-generateOpenApiDocs` to generate and upload
OpenAPI documentation.
- Removed redundant `@Autowired` annotations from `TempFileShutdownHook`
and `UnlockPDFFormsController`.
- Minor formatting and comment adjustments in YAML templates and
resource files.

- **Why the change was made:**  
- To introduce a clear `app/` directory hierarchy for core, common, and
proprietary modules, improving organization and maintainability.
- To ensure continuous integration and Docker builds continue to work
seamlessly with the reorganized structure.
- To automate OpenAPI documentation generation as part of the CI
pipeline.

---

## 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)

### 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.

.pre-commit-config.yaml

@@ -20,7 +20,7 @@ repos:
           - --skip="./.*,*.csv,*.json,*.ambr"
           - --quiet-level=2
         files: \.(html|css|js|py|md)$
-        exclude: (.vscode|.devcontainer|stirling-pdf/src/main/resources|Dockerfile|.*/pdfjs.*|.*/thirdParty.*|bootstrap.*|.*\.min\..*|.*diff\.js)
+        exclude: (.vscode|.devcontainer|app/core/src/main/resources|app/proprietary/src/main/resources|Dockerfile|.*/pdfjs.*|.*/thirdParty.*|bootstrap.*|.*\.min\..*|.*diff\.js)
   - repo: https://github.com/gitleaks/gitleaks
     rev: v8.27.2
     hooks:
@@ -34,3 +34,13 @@ repos:
       - id: trailing-whitespace
         files: ^.*(\.js|\.java|\.py|\.yml)$
         exclude: ^(.*/pdfjs.*|.*/thirdParty.*|bootstrap.*|.*\.min\..*|.*diff\.js|\.github/workflows/.*$)
+  # - repo: https://github.com/thibaudcolas/pre-commit-stylelint
+  #   rev: v16.21.1
+  #   hooks:
+  #     - id: stylelint
+  #       additional_dependencies:
+  #         - stylelint@16.21.1
+  #         - stylelint-config-standard@38.0.0
+  #         - "@stylistic/stylelint-plugin@3.1.3"
+  #       files: \.(css)$
+  #       args: [--fix]