lang updates plus --include-existing flag (#5212)

# Description of Changes

<!--
Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

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/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)

### 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.

scripts/translations/bulk_auto_translate.py

@@ -87,7 +87,7 @@ def get_language_completion(locales_dir: Path, language: str) -> Optional[float]
         return None
 
 
-def translate_language(language: str, api_key: str, batch_size: int, timeout: int, skip_verification: bool) -> Tuple[str, bool, str]:
+def translate_language(language: str, api_key: str, batch_size: int, timeout: int, skip_verification: bool, include_existing: bool) -> Tuple[str, bool, str]:
     """
     Translate a single language.
     Returns: (language_code, success, message)
@@ -105,6 +105,9 @@ def translate_language(language: str, api_key: str, batch_size: int, timeout: in
     if skip_verification:
         cmd.append('--skip-verification')
 
+    if include_existing:
+        cmd.append('--include-existing')
+
     try:
         result = subprocess.run(
             cmd,
@@ -170,6 +173,8 @@ Note: Requires OPENAI_API_KEY environment variable or --api-key argument.
                         help='Path to locales directory')
     parser.add_argument('--skip-verification', action='store_true',
                         help='Skip final completion verification for each language')
+    parser.add_argument('--include-existing', action='store_true',
+                        help='Also retranslate existing keys that match English (default: only translate missing keys)')
     parser.add_argument('--dry-run', action='store_true',
                         help='Show what would be translated without actually translating')
 
@@ -253,7 +258,8 @@ Note: Requires OPENAI_API_KEY environment variable or --api-key argument.
                 api_key,
                 args.batch_size,
                 args.timeout,
-                args.skip_verification
+                args.skip_verification,
+                args.include_existing
             ): lang
             for lang in languages
         }