feat(wiki): generate the course textbook into the wiki from modules/ via CI

- tools/build_wiki.py: host-agnostic generator — renders modules/** + capstone
  into wiki pages with a unit-by-unit _Sidebar, a Home TOC, and a _Footer;
  rewrites lab/ and repo-root links to absolute repo URLs (labs stay in the repo,
  linked not copied). Single source of truth stays in modules/.
- .gitea/workflows/sync-wiki.yml + .github/workflows/sync-wiki.yml: sync the wiki
  on every push to main touching modules/**, capstone/**, README, or the generator.
  Documented prerequisites: an Actions runner + a WIKI_TOKEN secret (+ GitHub wiki
  must be initialized once).
- tools/README.md: how to run the sync manually and via CI.
- README: "Read it as a book" pointer to the wiki.

The Gitea wiki has already been populated with the initial render.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

README.md

@@ -16,6 +16,15 @@ built on a branch and merged through review — exactly the motion the modules t
 
 ---
 
+## Read it as a book
+
+The lessons are rendered into the **[Wiki](../../wiki)** as a navigable textbook (unit-by-unit
+sidebar, one page per module). The wiki is generated from `modules/` and kept in sync
+automatically — it's build output, so read it there but **edit the lessons here in `modules/`**.
+See [`tools/`](tools/) for the generator and the sync workflows.
+
+---
+
 ## Who this is for
 
 IT professionals who are fluent in an AI chat window and comfortable with ops concepts — **not