🌐 Sync Translations + Update README Progress Table (#3703)

### Description of Changes

This Pull Request was automatically generated to synchronize updates to
translation files and documentation. Below are the details of the
changes made:

#### **1. Synchronization of Translation Files**
- Updated translation files (`messages_*.properties`) to reflect changes
in the reference file `messages_en_GB.properties`.
- Ensured consistency and synchronization across all supported language
files.
- Highlighted any missing or incomplete translations.

#### **2. Update README.md**
- Generated the translation progress table in `README.md`.
- Added a summary of the current translation status for all supported
languages.
- Included up-to-date statistics on translation coverage.

#### **Why these changes are necessary**
- Keeps translation files aligned with the latest reference updates.
- Ensures the documentation reflects the current translation progress.

---

Auto-generated by [create-pull-request][1].

[1]: https://github.com/peter-evans/create-pull-request

Co-authored-by: stirlingbot[bot] <195170888+stirlingbot[bot]@users.noreply.github.com>

README.md

@@ -145,7 +145,7 @@ Stirling-PDF currently supports 40 languages!
 | Romanian (Română) (ro_RO)                    | ![64%](https://geps.dev/progress/64)   |
 | Russian (Русский) (ru_RU)                    | ![76%](https://geps.dev/progress/76)   |
 | Serbian Latin alphabet (Srpski) (sr_LATN_RS) | ![49%](https://geps.dev/progress/49)   |
-| Simplified Chinese (简体中文) (zh_CN)         | ![95%](https://geps.dev/progress/95)   |
+| Simplified Chinese (简体中文) (zh_CN)         | ![99%](https://geps.dev/progress/99)   |
 | Slovakian (Slovensky) (sk_SK)                | ![57%](https://geps.dev/progress/57)   |
 | Slovenian (Slovenščina) (sl_SI)              | ![79%](https://geps.dev/progress/79)   |
 | Spanish (Español) (es_ES)                    | ![82%](https://geps.dev/progress/82)   |