fix(nortification): WebKit 系ブラウザにおいて通知の許可を求める popup が出ない問題の代替案

[uni-kakurenbo]

概要

Notification prompting can only be done from a user gesture.

と怒られてしまうので，Toast のクリックを経由するようにする

なぜこの PR を入れたいのか

closes: #4609

動作確認の手順

• Playwrgiht を用いて検証した (Playwright の制約上 denide になってしまうが，当該エラーが解消されていることは確認できた．)
• iPad (iOS 26) 実機を用いて期待通りの動作になっているか確かめた

UI 変更部分のスクリーンショット

PR を出す前の確認事項

• 動作確認ができている
• 自分で一度コードを眺めて自分的に問題はなさそう

[github-actions]

Preview (prod) → https://4875-prod.traq-preview.trapti.tech/
Preview (dev) → https://4875-dev.traq-preview.trapti.tech/

[codecov]

Codecov Report

❌ Patch coverage is 4.44444% with 43 lines in your changes missing coverage. Please review.
✅ Project coverage is 13.57%. Comparing base (f60357d) to head (14d783d).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
src/lib/notification/notification.ts	8.00%	23 Missing ⚠️
src/components/Toast/AToast.vue	0.00%	12 Missing ⚠️
src/store/ui/toast.ts	0.00%	6 Missing ⚠️
...mponents/Settings/BrowserTab/NotificationState.vue	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4875      +/-   ##
==========================================
+ Coverage   13.55%   13.57%   +0.01%     
==========================================
  Files         704      703       -1     
  Lines       31664    31691      +27     
  Branches      676      676              
==========================================
+ Hits         4293     4301       +8     
- Misses      27359    27378      +19     
  Partials       12       12              

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