feat(core): integrate google calendar sync (#14248)

fix #14170 
fix #13893 
fix #13673 
fix #13543 
fix #13308 
fix #7607




#### PR Dependency Tree


* **PR #14247**
  * **PR #14248** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

* **New Features**
* Integrations panel in Account Settings to link/unlink calendar
providers.
  * Collapsible settings wrapper for improved layout.

* **Improvements**
* Calendar system reworked: per-account calendar groups, simplified
toggles with explicit Save, richer event display (multi-dot date
indicators), improved event time/title handling across journal views.

* **Localization**
* Added calendar keys: save-error, no-journal, no-calendar; removed
legacy duplicate-error keys.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/i18n/src/resources/pl.json

@@ -2061,9 +2061,6 @@
   "com.affine.integration.calendar.unsubscribe": "Anuluj subskrypcję",
   "com.affine.integration.calendar.new-title": "Dodaj kalendarz przez URL",
   "com.affine.integration.calendar.new-url-label": "URL kalendarza",
-  "com.affine.integration.calendar.new-duplicate-error-title": "Jest to duplikat kalendarza",
-  "com.affine.integration.calendar.new-duplicate-error-content": "Ten subskrybowany kalendarz już istnieje w koncie subskrybowanych kalendarzy.",
-  "com.affine.integration.calendar.new-error": "Wystąpił błąd podczas dodawania kalendarza",
   "com.affine.integration.calendar.all-day": "Cały dzień",
   "com.affine.integration.calendar.new-doc": "Nowy dokument",
   "com.affine.integration.calendar.show-events": "Pokaż wydarzenia kalendarza",