feat(i18n): update German translation (#15159)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added a German invite notification title with a `{{count}}`
placeholder.
* **Bug Fixes**
* Improved German messaging for unsupported server/client version
mismatches, including a `{{requiredVersion}}` placeholder.
* **Updates**
* Refreshed German UI wording to consistently use “AFFiNE Sync” across
sign-in/onboarding, publishing/sharing, collaboration tips,
storage/autodelete guidance, and related confirmations (including
password reset and sign-out).
  * Updated the workspace chat sub-path label to “KI-Chat”.
* **Chores**
  * Updated German localization completeness score (99 → 100).
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/i18n/src/i18n-completenesses.json

@@ -2,7 +2,7 @@
   "ar": 95,
   "ca": 92,
   "da": 4,
-  "de": 99,
+  "de": 100,
   "el-GR": 91,
   "en": 100,
   "es-AR": 91,