feat(i18n): add scripts for locale translation and patching

- Implemented `fill-de-extended-gaps.js` to fill missing billing/orders keys in de-extended from de.
- Created `fill-i18n-deep.py` for deep translation of locale JSONs using deep-translator with fallback options.
- Added `fill-i18n-locales.js` to translate locale JSONs and write overrides for untranslated keys.
- Introduced `fix-en-leaks.py` to translate keys that still match the en-US merge, addressing English leaks.
- Developed `patch-de-ch-swiss.js` to replace 'ß' with 'ss' in de-CH.json without deleting existing entries.
- Created `patch-en-gb-au.js` to apply UK/AU spelling corrections in en-GB and en-AU locales.
- Added shell scripts `run-fix-en-leaks.sh` and `run-i18n-deep-fill.sh` for sequential execution of translation tasks.
- Implemented `update-i18n-todo-stats.js` to update statistics in the I18N_TODO.md file based on translation completeness.

mobile-app/gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 # composeApp (Play Store / „Über die App“-Build)
-appVersionCode = "5"
-appVersionName = "1.2.1"
+appVersionCode = "6"
+appVersionName = "1.3.0"
 agp = "9.2.1"
 android-compileSdk = "35"
 android-minSdk = "24"