fix(frontend): 絵文字管理画面で絵文字が表示されないことがある問題を修正

[kakkokari-gtyih]

What

EmojiDetailedの画像URLをそのまま使うように（リモートはメディアプロキシ経由）

Why

Fix #15127

Additional info (optional)

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

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 19.32%. Comparing base (e8bf628) to head (02ac187).
Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
...kages/frontend/src/pages/custom-emojis-manager.vue	0.00%	3 Missing ⚠️
packages/frontend/src/pages/emoji-edit-dialog.vue	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           develop   #15128       +/-   ##
============================================
- Coverage    39.96%   19.32%   -20.64%     
============================================
  Files         1563      728      -835     
  Lines       197752   103809    -93943     
  Branches      3634      991     -2643     
============================================
- Hits         79031    20066    -58965     
+ Misses      118116    83189    -34927     
+ Partials       605      554       -51     

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[syuilo]

🙏