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

paseo/.env.example

@@ -2,6 +2,9 @@
 #
 #   cp .env.example .env
 
+# Container hostname, shown as the host label in the web UI.
+SERVICE_HOSTNAME=paseo
+
 # Password for the daemon API and web UI. Also the paseo user's login password,
 # so it is what `sudo` asks for inside a terminal.
 # Generate one with: openssl rand -base64 24
@@ -23,7 +26,3 @@ AGENTS=claude codex
 # these directly, so no `git config` step is needed.
 GIT_NAME=
 GIT_EMAIL=
-
-# Container hostname, shown as the host label in the web UI. Also passed in as
-# HOST -- the name zsh's prompt shows.
-SERVICE_HOSTNAME=paseo