fix: preserve HTML content when replying to HTML emails (#856)

* fix: preserve HTML content when replying to HTML emails (#728)

Reply was using curMail.text (plain text) instead of curMail.message (HTML),
causing loss of original email formatting. Forward already used HTML correctly.

Now reply prefers HTML content with plain text fallback, matching forward behavior.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: add vitest unit tests for reply/forward mail logic

Extract buildReplyModel and buildForwardModel into testable utility
functions and add 13 unit tests covering HTML content preservation,
plain text fallback, sender parsing, and subject formatting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: remove unnecessary vitest exclude config

The e2e files have been deleted, so the test.exclude config in
vite.config.js is no longer needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: revert unnecessary trailing comma in vite.config.js

Restore vite.config.js to match main exactly — no changes needed
for this PR.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: add e2e screenshots for PR review

Screenshots from local Playwright test showing:
1. HTML email rendered correctly in inbox
2. Reply editor preserving HTML content in blockquote

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: remove temporary test screenshots

Screenshots have been posted as PR comment, no longer needed in tree.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: use html contentType for HTML email replies instead of rich

wangEditor (rich text editor) strips block-level HTML tags inside
blockquote, losing all formatting. Use contentType 'html' for HTML
email replies (matching forward behavior) so content is edited as
raw HTML in a textarea, preserving all formatting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: update e2e screenshots showing HTML formatting preserved

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: remove temporary screenshots from tree

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: add SMTP send flow E2E screenshots with mailpit

Screenshots showing complete SMTP HTML email reply flow:
1. View rich HTML email (gradient headers, tables, badges)
2. Reply compose with HTML mode (textarea, not wangEditor)
3. Sent box showing preserved HTML formatting
4. Mailpit inbox receiving the SMTP email
5. Mailpit email detail with full HTML rendering

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: remove temporary SMTP test screenshots from tree

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -20,6 +20,7 @@
 - fix: |文档| 修复 User Mail API 文档中错误使用 `x-admin-auth` 的问题，改为正确的 `x-user-token`
 - fix: |前端| 修复暗色主题下邮件内容文字看不清的问题，优化纯文本邮件和 Shadow DOM 渲染的暗色模式样式
 - docs: |文档| 新增 Admin 删除邮件、删除邮箱地址、清空收件箱、清空发件箱 API 文档
+- fix: |前端| 修复回复 HTML 格式邮件时丢失原邮件 HTML 内容的问题，优先使用 HTML 原文而非纯文本
 
 ### Improvements