feat(conversion): add eBook to PDF via Calibre (EPUB/MOBI/AZW3/FB2/TXT/DOCX) (#4644)

This pull request adds support for converting common eBook formats
(EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre. It introduces a
new API endpoint and updates the configuration, dependency checks, and
documentation to support this feature. Additionally, it includes related
UI and localization changes.

**New eBook to PDF conversion feature:**

* Added `ConvertEbookToPDFController` with a new
`/api/v1/convert/ebook/pdf` endpoint to handle eBook to PDF conversion
using Calibre, supporting options like embedding fonts, including table
of contents, and page numbers.
* Introduced `ConvertEbookToPdfRequest` model for handling conversion
requests and options.

**Configuration and dependency management:**

* Updated `RuntimePathConfig`, `ApplicationProperties`, and
`ExternalAppDepConfig` to support Calibre's executable path
configuration and dependency checking, ensuring Calibre is available and
correctly integrated.
[[1]](diffhunk://#diff-68c561052c2376c3d494bf11dd821958acd9917b1b2d33a7195ca2d6df7ec517R24)
[[2]](diffhunk://#diff-68c561052c2376c3d494bf11dd821958acd9917b1b2d33a7195ca2d6df7ec517R61)
[[3]](diffhunk://#diff-68c561052c2376c3d494bf11dd821958acd9917b1b2d33a7195ca2d6df7ec517R72-R74)
[[4]](diffhunk://#diff-1c357db0a3e88cf5bedd4a5852415fadad83b8b3b9eb56e67059d8b9d8b10702R359)
[[5]](diffhunk://#diff-8932df49d210349a062949da2ed43ce769b0f107354880a78103664f008f849eR26-R34)
[[6]](diffhunk://#diff-8932df49d210349a062949da2ed43ce769b0f107354880a78103664f008f849eR48)
[[7]](diffhunk://#diff-8932df49d210349a062949da2ed43ce769b0f107354880a78103664f008f849eR63-R68)
[[8]](diffhunk://#diff-8932df49d210349a062949da2ed43ce769b0f107354880a78103664f008f849eR132)
* Registered the new endpoint and tool group in `EndpointConfiguration`,
including logic to enable/disable the feature based on Calibre's
presence.
[[1]](diffhunk://#diff-3cddb66d1cf93eeb8103ccd17cee8ed006e0c0ee006d0ee1cf42d512f177e437R260)
[[2]](diffhunk://#diff-3cddb66d1cf93eeb8103ccd17cee8ed006e0c0ee006d0ee1cf42d512f177e437R440-R442)
[[3]](diffhunk://#diff-3cddb66d1cf93eeb8103ccd17cee8ed006e0c0ee006d0ee1cf42d512f177e437L487-R492)

**Documentation and localization:**

* Updated the `README.md` to mention eBook to PDF conversion support.
* Added UI route and form for eBook to PDF conversion in the web
controller.
* Added English and German localization strings for the new feature,
including descriptions, labels, and error messages.
[[1]](diffhunk://#diff-ee1c6999a33498cfa3abba4a384e73a8b8269856899438de80560c965079a9fdR617-R620)
[[2]](diffhunk://#diff-482633b22866efc985222c4a14efc5b7d2487b59f39b953f038273a39d0362f7R617-R620)
[[3]](diffhunk://#diff-482633b22866efc985222c4a14efc5b7d2487b59f39b953f038273a39d0362f7R1476-R1485)


## 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.

---------

Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

testing/allEndpointsRemovedSettings.yml

@@ -158,7 +158,7 @@ ui:
   languages: [] # If empty, all languages are enabled. To display only German and Polish ["de_DE", "pl_PL"]. British English is always enabled.
 
 endpoints:
-  toRemove: [crop, merge-pdfs, multi-page-layout, overlay-pdfs, pdf-to-single-page, rearrange-pages, remove-image-pdf, remove-pages, rotate-pdf, scale-pages, split-by-size-or-count, split-pages, split-pdf-by-chapters, split-pdf-by-sections, add-password, add-watermark, auto-redact, cert-sign, get-info-on-pdf, redact, remove-cert-sign, remove-password, sanitize-pdf, validate-signature, file-to-pdf, html-to-pdf, img-to-pdf, markdown-to-pdf, pdf-to-csv, pdf-to-html, pdf-to-img, pdf-to-markdown, pdf-to-pdfa, pdf-to-presentation, pdf-to-text, pdf-to-word, pdf-to-xml, url-to-pdf, add-image, add-page-numbers, add-stamp, auto-rename, auto-split-pdf, compress-pdf, decompress-pdf, extract-image-scans, extract-images, flatten, ocr-pdf, remove-blanks, repair, replace-invert-pdf, show-javascript, update-metadata, filter-contains-image, filter-contains-text, filter-file-size, filter-page-count, filter-page-rotation, filter-page-size, add-attachments] # list endpoints to disable (e.g. ['img-to-pdf', 'remove-pages'])
+  toRemove: [ebook-to-pdf, crop, merge-pdfs, multi-page-layout, overlay-pdfs, pdf-to-single-page, rearrange-pages, remove-image-pdf, remove-pages, rotate-pdf, scale-pages, split-by-size-or-count, split-pages, split-pdf-by-chapters, split-pdf-by-sections, add-password, add-watermark, auto-redact, cert-sign, get-info-on-pdf, redact, remove-cert-sign, remove-password, sanitize-pdf, validate-signature, file-to-pdf, html-to-pdf, img-to-pdf, markdown-to-pdf, pdf-to-csv, pdf-to-html, pdf-to-img, pdf-to-markdown, pdf-to-pdfa, pdf-to-presentation, pdf-to-text, pdf-to-word, pdf-to-xml, url-to-pdf, add-image, add-page-numbers, add-stamp, auto-rename, auto-split-pdf, compress-pdf, decompress-pdf, extract-image-scans, extract-images, flatten, ocr-pdf, remove-blanks, repair, replace-invert-pdf, show-javascript, update-metadata, filter-contains-image, filter-contains-text, filter-file-size, filter-page-count, filter-page-rotation, filter-page-size, add-attachments] # list endpoints to disable (e.g. ['img-to-pdf', 'remove-pages'])
   groupsToRemove: [] # list groups to disable (e.g. ['LibreOffice'])
 
 metrics:

testing/endpoints.txt

@@ -44,6 +44,7 @@
 /api/v1/convert/markdown/pdf
 /api/v1/convert/img/pdf
 /api/v1/convert/html/pdf
+/api/v1/convert/ebook/pdf
 /api/v1/convert/file/pdf
 /api/v1/general/split-pdf-by-sections
 /api/v1/general/split-pdf-by-chapters

testing/webpage_urls_full.txt

@@ -14,6 +14,7 @@
 /compare
 /compress-pdf
 /crop
+/ebook-to-pdf
 /extract-image-scans
 /extract-images
 /extract-page
@@ -62,4 +63,4 @@
 /stamp
 /validate-signature
 /view-pdf
-/swagger-ui/index.html
+/swagger-ui/index.html