feat: support dev-only nodes (#8359)

## Summary

Support `dev_only` property to node definitions that hides nodes from
search and menus unless dev mode is enabled. Dev-only nodes display a
"DEV" badge when visible.

This functionality is primarily intended to support unit-testing nodes
on Comfy Cloud, but also has other uses.

## Changes

- **What**: Nodes flagged as dev_only in the node schema will only
appear in search and menus if Dev Mode is on.

## Screenshots (if applicable)

With Dev Mode off:
<img width="2189" height="1003" alt="image"
src="https://github.com/user-attachments/assets/a08e1fd7-dca9-4ce1-9964-5f4f3b7b95ac"
/>

With Dev Mode on:
<img width="2201" height="1066" alt="image"
src="https://github.com/user-attachments/assets/7fe6cd1f-f774-4f48-b604-a528e286b584"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8359-feat-support-dev-only-nodes-2f66d73d36508102839ee7cd66a26129)
by [Unito](https://www.unito.io)

src/locales/en/main.json

@@ -121,6 +121,7 @@
     "customize": "Customize",
     "experimental": "BETA",
     "deprecated": "DEPR",
+    "devOnly": "DEV",
     "loadWorkflow": "Load Workflow",
     "goToNode": "Go to Node",
     "setAsBackground": "Set as Background",