feat: bake frontend commit hash into build (#9832)

## Summary

Bake the frontend git commit hash into the build so it no longer needs
to be fetched from the server via `/api/system_stats`.

## Changes

- **What**: Add `__COMFYUI_FRONTEND_COMMIT__` build-time constant (via
Vite `define`) sourced from `git rev-parse HEAD` at build time. Falls
back to `"unknown"` if git is unavailable. `SystemStatsPanel` uses this
baked-in value for the "Frontend Version" row in cloud mode instead of
the server-provided `comfyui_frontend_version` field.

## Testing
Confirmed to display the actual commit.
<img width="1448" height="908" alt="Screenshot 2026-03-12 at 7 09 52 PM"
src="https://github.com/user-attachments/assets/2b42348a-5c3e-4509-aa84-1a259bba5f3f"
/>


## Review Focus

- The `getDisplayValue` override for `comfyui_frontend_version` —
cleanest way to swap the data source without restructuring the column
system.
- No cloud-side changes needed: the `sync-frontend-build` workflow
already checks out the frontend repo at the exact commit ref, so `git
rev-parse HEAD` returns the correct hash.

eslint.config.ts

@@ -24,6 +24,7 @@ const extraFileExtensions = ['.vue']
 const commonGlobals = {
   ...globals.browser,
   __COMFYUI_FRONTEND_VERSION__: 'readonly',
+  __COMFYUI_FRONTEND_COMMIT__: 'readonly',
   __DISTRIBUTION__: 'readonly',
   __IS_NIGHTLY__: 'readonly'
 } as const