feat(server): add RSS feed support for comment subscriptions

[Copilot]

Implements RSS 2.0 feed generation for comment subscriptions, enabling users to track comments via feed readers.

Changes

• RSS feed endpoint: Added GET /api/comment?type=rss with optional url, count, and lang parameters
• RSS dependency: Added [email protected] package for standards-compliant feed generation
• i18n support: Detects language from lang parameter, generates localized feed titles ("评论于" vs "commented on")
• XML response handling: RSS requests bypass JSON serialization in getAction() to return proper XML
• Date handling: Preserves insertedAt Date objects through formatting pipeline for accurate RSS timestamps
• URL fallback: Graceful degradation when protocol/host unavailable in request context

Usage

GET /api/comment?type=rss&count=20&url=/post/article&lang=zh-cn

Returns RSS 2.0 XML with:

• Comment author, rendered HTML content
• Article URL with comment anchor (#objectId)
• Publication date, unique GUID
• Max 100 items, approved comments only

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• metadata.tencentyun.com
  • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/waline/waline/packages/server/development.js 9090 (dns block)
  • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/waline/waline/packages/server/development.js 9191 (dns block)
• oauth.lithub.cc
  • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/waline/waline/packages/server/development.js 9191 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

帮我提个 PR，让 Server 评论返回支持 RSS 功能

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