docs: add comprehensive phpBB research and gap analysis
Deep research into phpBB's feature set, common complaints, decline
reasons, and lessons from modern competitors (Discourse, Flarum,
XenForo). Includes prioritized gap analysis comparing atBB's current
feature set against phpBB's, with actionable recommendations.
Key findings:
- AT Proto identity is atBB's biggest advantage (spam resistance,
portable identity, data ownership)
- Critical missing features: rich text/markdown, unread tracking,
notifications, search, post reporting
- phpBB's permission complexity is a cautionary tale — keep it simple
- Discourse's trust levels are worth adopting in simplified form
- Real-time updates via firehose + HTMX SSE would be a differentiator
https://claude.ai/code/session_012nLGUeocmDKttJz1VYFPPA