enhance(backend): アクセストークンでアカウントを作成できるように

[eternal-flame-AD]

What

Fixes #14959

Why

Additional info (optional)

Checklist

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.33333% with 6 lines in your changes missing coverage. Please review.

Project coverage is 41.66%. Comparing base (eed45c7) to head (f767c22).

Files with missing lines	Patch %	Lines
.../src/server/api/endpoints/admin/accounts/create.ts	33.33%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #14989 +/- ## =========================================== + Coverage 39.97% 41.66% +1.69% =========================================== Files 1561 1565 +4 Lines 197256 203042 +5786 Branches 3607 3640 +33 =========================================== + Hits 78849 84597 +5748 - Misses 117835 117839 +4 - Partials 572 606 +34 ```

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[github-actions[bot]]

このPRによるapi.jsonの差分

差分はこちら

```diff --- base +++ head @@ -2050,6 +2050,7 @@ "ACCESS_DENIED": { "value": { "error": { + "httpStatusCode": 403, "message": "Access denied.", "code": "ACCESS_DENIED", "id": "1fb7cb09-d46a-4fff-b8df-057708cce513" @@ -2059,6 +2060,7 @@ "INCORRECT_INITIAL_PASSWORD": { "value": { "error": { + "httpStatusCode": 401, "message": "Initial password is incorrect.", "code": "INCORRECT_INITIAL_PASSWORD", "id": "97147c55-1ae1-4f6f-91d6-e1c3e0e76d62" ``` [Get diff files from Workflow Page](https://github.com/misskey-dev/misskey/actions/runs/11883769176)