Forum integration: Flarum extension, local test stack, embedded comments

- forum/extension: oc:import command (archived comments -> one thread per
  machine) and embed styling
- forum/docker: local Flarum 2 test stack
- site: optional params.forum.url adds a Forum menu entry and shows the
  machine thread in the Comments tab

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDRjtmAiNpo5mK5N3d7QwZ

README.md

@@ -10,6 +10,8 @@ Static rebuild of old-computers.com with [Hugo](https://gohugo.io/) (0.158 or ne
 | `static/media/` | generated (copied images and documents) |
 | `data/slugs.json` | generated, keeps URLs stable between runs — do not delete |
 | `content/post/` | written by hand: news posts, see below |
+| `data/forum.json` | machine → forum thread map, written by the forum import (absent = no forum) |
+| `forum/` | forum extension, local test stack, install notes |
 | `content/_index.md`, `layouts/`, `assets/`, `hugo.toml`, `tools/` | written by hand |
 | `build/`, `public/` | build output (`make build`, `hugo server`), not versioned |
 
@@ -39,6 +41,14 @@ sends to `/search/`, where results can be filtered by section. Content pages are
 visitor-comments tabs are not. `hugo server` has no index: use `make build` and serve `build/`
 to try the search locally.
 
+## Forum and comments
+
+A [Flarum](https://flarum.org/) forum can run next to the site and serve as its comment system:
+with `params.forum.url` set in `hugo.toml`, the menu gets a Forum entry and the Comments tab of
+each machine shows that machine's forum thread (archived comments first, new replies after).
+With the url empty the site has no forum and shows the archived comments as static text.
+Everything about the forum is in [`forum/README.md`](forum/README.md).
+
 ## Usage
 
     make content   # regenerate from ../oc (OC=path to use another location)