chore: drop HOST overrides, move known issue to docs, tidy comments and gitignores

- Remove HOST=${SERVICE_HOSTNAME} from code-server, code-server-lsio and paseo; hostname: alone sets the name
- Move SERVICE_HOSTNAME to the top of their .env.example to match compose order
- Drop the openclaw ARM64 Chromium note from its README; docs/openclaw covers it
- List CUSTOM_USER in webtop's setup step
- Trim reasoning from diun and paseo comments
- Delete stale gitea and gitea-mirror .gitignore files
- Add TODO.md for remaining naming and README issues

openclaw/README.md

@@ -93,8 +93,3 @@ user.
 `ghcr.io/openclaw/openclaw:latest-browser` is the latest stable release with
 Playwright Chromium built in, published by the project's release automation.
 Upstream publishes no major tag.
-
-On ARM64, release 2026.9.8 cannot find its bundled Chromium ("No supported
-browser found"); the fix is merged upstream but not yet released. Everything
-except browser automation works meanwhile, and the browser starts working on
-the first pull after a release that contains the fix, with no change here.