Cloud Auth Backport (#6195)

## Summary

Backports Firebase authentication with cloud environments.

Changes only work when developing for cloud environment locally.

## Changes

- Router guards to force unauthenticated users to sign in.
- Configure auth headers for REST and Websocket connections.
- Code implemented in a way that enables build tree-shaking based on
distribution
- Updates to build process to build cloud distribution and simplify
development workflow

## Review Focus

1. Idomatic Vue/codebase patterns.
2. Build logic (please double check that I integrated correctly with:
https://github.com/Comfy-Org/ComfyUI_frontend/blob/rh-test/vite.config.mts)

## Screenshots (if applicable)




https://github.com/user-attachments/assets/ee4ea3f7-afa6-4da0-ba43-d62ed8ba4e18





┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6195-Feat-cloud-auth-backport-2946d73d365081f395f5f2a89fb7d800)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: GitHub Action <action@github.com>

.env_example

@@ -5,6 +5,10 @@ PLAYWRIGHT_TEST_URL=http://localhost:5173
 
 # Proxy target of the local development server
 # Note: localhost:8188 does not work.
+# Cloud auto-detection: Setting this to any *.comfy.org URL automatically enables
+# cloud mode (DISTRIBUTION=cloud) without needing to set DISTRIBUTION separately.
+# Examples: https://testcloud.comfy.org/, https://stagingcloud.comfy.org/,
+#           https://pr-123.testenvs.comfy.org/, https://cloud.comfy.org/
 DEV_SERVER_COMFYUI_URL=http://127.0.0.1:8188
 
 # Allow dev server access from remote IP addresses.