enhance: stats apiの重い処理をスキップできるように

[kakkokari-gtyih]

What

リアクションカウントのぶぶんをスキップして/stats APIを返せるようにした

Why

https://github.com/misskey-dev/misskey/issues/4880#issuecomment-2454182256 （根本解決ではないが、暫定対応としてはこれで十分かと）

Additional info (optional)

Checklist

• [x] Read the contribution guide
• [ ] Test working in a local environment
• [ ] (If needed) Add story of storybook
• [x] (If needed) Update CHANGELOG.md
• [ ] (If possible) Add tests

[github-actions[bot]]

このPRによるapi.jsonの差分

差分はこちら

```diff --- base +++ head @@ -401,6 +401,9 @@ "enableServerMachineStats": { "type": "boolean" }, + "enableEnhancedServerStats": { + "type": "boolean" + }, "enableIdenticonGeneration": { "type": "boolean" }, @@ -654,6 +657,7 @@ "enableChartsForFederatedInstances", "enableStatsForFederatedInstances", "enableServerMachineStats", + "enableEnhancedServerStats", "enableIdenticonGeneration", "manifestJsonOverride", "policies", @@ -14288,6 +14292,9 @@ "enableServerMachineStats": { "type": "boolean" }, + "enableEnhancedServerStats": { + "type": "boolean" + }, "enableIdenticonGeneration": { "type": "boolean" }, ``` [Get diff files from Workflow Page](https://github.com/misskey-dev/misskey/actions/runs/12034440971)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 30.55556% with 25 lines in your changes missing coverage. Please review.

Project coverage is 39.96%. Comparing base (a77ad7a) to head (43ac9fc). Report is 6 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/frontend/src/pages/admin/performance.vue	0.00%	16 Missing :warning:
...kend/src/server/api/endpoints/admin/update-meta.ts	20.00%	4 Missing :warning:
packages/backend/src/server/api/endpoints/stats.ts	20.00%	4 Missing :warning:
...ges/backend/src/server/api/endpoints/admin/meta.ts	80.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #15062 +/- ## =========================================== - Coverage 39.96% 39.96% -0.01% =========================================== Files 1563 1563 Lines 197744 197778 +34 Branches 3631 3632 +1 =========================================== + Hits 79027 79034 +7 - Misses 118112 118139 +27 Partials 605 605 ```

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