Replace custom code-server (9GB) with upstream LinuxServer image (~1GB)

Drop the custom Dockerfile.code-server that bundled Claude Code CLI,
Python/MkDocs tooling, and build-essential on top of codercom base.
Switch to the already-mirrored linuxserver/code-server image instead.

- Both compose files: use code-server:latest, LinuxServer env vars
  (PUID/PGID/DEFAULT_WORKSPACE), port 8443, /config mount layout
- Nginx configs + templates: proxy to :8443 instead of :8080
- API env default: CODE_SERVER_URL updated to :8443
- build-and-push.sh: remove --include-code-server flag
- upgrade.sh: remove code-server conditional rebuild + registry fallback
- install.sh: add --ignore-pull-failures for optional missing images
- .env.example, CCP templates, bunker-ops template: updated

Bunker Admin

mkdocs/docs/docs/getting-started/environment-variables.md

@@ -315,8 +315,7 @@ Self-hosted Git repository. Optional service.
 | Variable | Default | Description |
 |----------|---------|-------------|
 | `CODE_SERVER_PORT` | `8888` | Code Server web UI port. |
-| `CODE_SERVER_URL` | `http://code-server:8080` | Internal container URL. |
-| `USER_NAME` | `coder` | User account inside the Code Server container. |
+| `CODE_SERVER_URL` | `http://code-server-changemaker:8443` | Internal container URL. |
 
 ---