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

webtop/README.md

@@ -14,7 +14,7 @@ takes a few minutes longer before the desktop answers.
 
 ## Setup
 
-1. Set `PASSWORD`.
+1. Set `CUSTOM_USER` and `PASSWORD`.
 2. Map the domain to port `3000` and deploy.
 3. Open the domain and log in with `CUSTOM_USER` / `PASSWORD`.