Add anti-spam moderation for first posts with links

[drusepth]

Fixes #

User-facing changes

• First-time forum posters who include links in their initial post now have that post held for moderator review, along with their topic and user account
• Forum staff (moderators and admins) are exempt from this automatic moderation
• Moderators receive Discord notifications when posts are held for review, with one notification per user while they have pending posts in the queue
• Topics held for moderation are announced on Discord once approved by a moderator, rather than at creation time

Implementation notes

• Added contains_link? method to detect common link formats (http/https URLs, www links, and markdown-style links) in post content
• Implemented hold_first_post_with_links_for_moderation callback that:
  • Checks if a post is a user's first post and contains a link
  • Holds the post, its topic, and the user's account for moderation
  • Ensures subsequent posts by a pending user are also held until approval
• Added cascade_pending_moderation_to_topic to sync topic moderation state with its first post
• Created NotifyDiscordOfPendingPostJob to ping the moderation Discord channel when posts enter the queue
• Modified NotifyDiscordOfThreadJob to:
  • Skip announcing topics held for moderation at creation time
  • Announce them once a moderator approves them instead
  • Avoid duplicate announcements if approval happens within the 1-minute creation delay
• Added logic to detect whether a thread went through the moderation queue using PostModerationRecord
• Updated .gitignore to exclude locally-installed gems in /vendor/bundle

Testing

• Added comprehensive test suite in test/models/forum_first_post_moderation_test.rb covering:
  • First posts with links are held for moderation
  • First posts without links are approved normally
  • Subsequent posts from users with existing posts are approved
  • Replies to others' topics don't affect the topic's moderation state
  • Subsequent posts by held users are also held
  • Forum staff bypass the moderation check
  • Approving a held post cascades approval to the topic and user
  • Link detection for various formats
  • Discord notification behavior (single ping per user, no duplicate pings)
• Added test suite in test/jobs/notify_discord_of_thread_job_test.rb covering:
  • Approved threads are announced
  • Held threads are not announced at creation
  • Held threads are announced once when approved
  • No duplicate announcements within the 1-minute window

All new tests pass and cover the anti-spam workflow end-to-end.

https://claude.ai/code/session_01UxYdrUQipvTQzr9v2ENbhv