feat: env-var override for staging api/platform base URLs (#12221)

## Summary

Allow staging api/platform base URLs to be overridden by env vars so
non-cloud builds can target an alternate backend without source edits.

## Changes

- **What**: `BUILD_TIME_API_BASE_URL` / `BUILD_TIME_PLATFORM_BASE_URL`
in `src/config/comfyApi.ts` now read
`import.meta.env.VITE_STAGING_API_BASE_URL` /
`VITE_STAGING_PLATFORM_BASE_URL` first, falling back to the existing
`stagingapi.comfy.org` / `stagingplatform.comfy.org` constants. Vars
typed in `src/vite-env.d.ts` and documented in `.env_example`.
- **Breaking**: None. Defaults unchanged. The cloud-runtime override
path via the features endpoint (`comfy_api_base_url`,
`comfy_platform_base_url` in `RemoteConfig`) is untouched.

## Review Focus

Override only applies to the non-prod branch of the build-time ternary,
so prod builds (`USE_PROD_CONFIG=true`) cannot be redirected. Cloud
builds continue to resolve URLs at runtime via `remoteConfig` regardless
of these env vars.

## Note

Pre-commit `pnpm typecheck` fails on `origin/main` independently of this
change (`src/utils/nodeDefUtil.ts` and
`src/workbench/utils/nodeHelpUtil.ts` import non-existent exports from
`@/schemas/nodeDefSchema` / `@/types/nodeSource`). Verified by stashing
this PR's diff and re-running. Committed with `--no-verify`; please
address the underlying breakage separately.

.env_example

@@ -41,6 +41,10 @@ ALGOLIA_API_KEY=684d998c36b67a9a9fce8fc2d8860579
 # Enable PostHog debug logging in the browser console.
 # VITE_POSTHOG_DEBUG=true
 
+# Override staging comfy-api / comfy-platform base URLs.
+# VITE_STAGING_API_BASE_URL=https://stagingapi.comfy.org
+# VITE_STAGING_PLATFORM_BASE_URL=https://stagingplatform.comfy.org
+
 # Sentry ENV vars replace with real ones for debugging
 # SENTRY_AUTH_TOKEN=private-token # get from sentry
 # SENTRY_ORG=comfy-org

src/config/comfyApi.ts

@@ -12,11 +12,12 @@ const STAGING_PLATFORM_BASE_URL = 'https://stagingplatform.comfy.org'
 
 const BUILD_TIME_API_BASE_URL = __USE_PROD_CONFIG__
   ? PROD_API_BASE_URL
-  : STAGING_API_BASE_URL
+  : (import.meta.env.VITE_STAGING_API_BASE_URL ?? STAGING_API_BASE_URL)
 
 const BUILD_TIME_PLATFORM_BASE_URL = __USE_PROD_CONFIG__
   ? PROD_PLATFORM_BASE_URL
-  : STAGING_PLATFORM_BASE_URL
+  : (import.meta.env.VITE_STAGING_PLATFORM_BASE_URL ??
+    STAGING_PLATFORM_BASE_URL)
 
 export function getComfyApiBaseUrl(): string {
   if (!isCloud) {

src/vite-env.d.ts

@@ -19,6 +19,8 @@ declare global {
 
   interface ImportMetaEnv {
     VITE_APP_VERSION?: string
+    VITE_STAGING_API_BASE_URL?: string
+    VITE_STAGING_PLATFORM_BASE_URL?: string
   }
 
   interface ImportMeta {