fix(backend): FreeBSDで起動できない問題を修正

[kakkokari-gtyih]

What

• @napi-rs/canvasがFreeBSDに対応していないためcanvasに変更
• FreeBSDでの起動の障害となっていたクラスの参照を変更

Why

Fix #12764

Additional info (optional)

FreeBSDの環境がないので検証してない
（ https://activitypub.software/TransFem-org/Sharkey/-/merge_requests/887 では起動できることが確認されている）

Checklist

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

[github-actions]

このPRによるapi.jsonの差分
差分はありません。
Get diff files from Workflow Page

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 42.12%. Comparing base (f3a4434) to head (710aa0b).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/backend/src/misc/gen-identicon.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #15418   +/-   ##
========================================
  Coverage    42.12%   42.12%           
========================================
  Files         1609     1609           
  Lines       161803   161803           
  Branches      4083     4084    +1     
========================================
+ Hits         68161    68166    +5     
+ Misses       93194    93157   -37     
- Partials       448      480   +32     

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[Mar0xy]

For information about @napi-rs/canvas:

@napi-rs/canvas uses Skia which does not at all support FreeBSD OOTB without modifications/patching. See attached image from a Google dev saying that supporting FreeBSD is not planned.

[kakkokari-gtyih]

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