feat: basic caldav support (#14372)

fix #13531 

#### PR Dependency Tree


* **PR #14372** 👈

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**
* CalDAV calendar integration: link and sync CalDAV-compatible calendars
(discovery, listing, event sync).
* New UI flow and dialog to link CalDAV accounts with provider
selection, credentials, and display name.

* **API / Config**
* Server exposes CalDAV provider presets in config and new GraphQL
mutation to link CalDAV accounts.
  * New calendar config section for CalDAV with validation and defaults.

* **Tests**
  * Comprehensive CalDAV integration test suite added.

* **Chores**
* Removed analytics tokens from build configuration and reduced Cloud
E2E test shards.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/build-test.yml

@@ -1016,21 +1016,12 @@ jobs:
       fail-fast: false
       matrix:
         tests:
-          - name: 'Cloud E2E Test 1/10'
+          - name: 'Cloud E2E Test 1/2'
             shard: 1
-            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=1/10
-          - name: 'Cloud E2E Test 2/10'
+            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=1/2
+          - name: 'Cloud E2E Test 2/2'
             shard: 2
-            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=2/10
-          - name: 'Cloud E2E Test 3/10'
-            shard: 3
-            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=3/10
-          - name: 'Cloud E2E Test 4/10'
-            shard: 4
-            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=4/10
-          - name: 'Cloud E2E Test 5/10'
-            shard: 5
-            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=5/10
+            script: yarn affine @affine-test/affine-cloud e2e --forbid-only --shard=2/2
           - name: 'Cloud Desktop E2E Test'
             shard: desktop
             script: |