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

hugo.toml

@@ -19,6 +19,11 @@ capitalizeListTitles = false
   listPosts = 10
   description = "The Old-Computers.com museum of computers, consoles and pongs, rebuilt from the Wayback Machine archive."
 
+  # Forum (Flarum, see forum/README.md). Empty url = no forum: no menu entry, and machine pages
+  # show the archived comments as static text. With a url, the Comments tab shows the forum thread.
+  [params.forum]
+    url = ""
+
 [taxonomies]
   category = "categories"
   type = "types"