Summary

Two collaboration/inspection features:

1. Comments on issues and merge requests — threaded comments on issue and MR detail pages (author + timestamp, server-rendered Qute, new comments table + Flyway migration).
2. Per-commit diff view — from the commits tab, clicking a commit opens a detail page showing the diff introduced by that commit (files changed, added/removed lines).

Motivation

No discussion surface today (no comments) and no way to inspect what a single commit changed. Both are table-stakes for a Git platform.

Docs to update (AGENTS.md rule)

• docs/users/ — comment workflow, viewing commit changes
• docs/admins/ — new comments table
• docs/maintainers/ — implementation notes
• Root README.md feature list

Notes

• Test-first: failing test before each capability.