feat: Enable system notifications on cloud (#7277)

Re-enables the system notification popup for cloud distribution,
allowing cloud devs to notify cloud users about new features and updates
without requiring a new release.

Cloud now fetches release notes from the "cloud" project (instead of
"comfyui") and uses the `cloud_version` field for version comparison.
Since cloud versions are git hashes rather than semver, a helper handles
both formats gracefully.

The "What's New" popup is enabled for cloud, while the update toast and
red dot indicator remain desktop-only since cloud auto-updates and
doesn't require user action.

You can test this by doing `pnpm dev:cloud` and you will see a
notification I added (for testing):

<img width="1891" height="2077" alt="image"
src="https://github.com/user-attachments/assets/6599a6dc-a3e1-406f-a22d-14262be1f258"
/>

Content is controlled by non-devs at cms.comfy.org.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7277-feat-Enable-system-notifications-on-cloud-2c46d73d365081bcb33cd79ec18faefe)
by [Unito](https://www.unito.io)

tests-ui/tests/store/systemStatsStore.test.ts

@@ -17,6 +17,8 @@ vi.mock('@/utils/envUtil', () => ({
   isElectron: vi.fn()
 }))
 
+vi.mock('@/platform/distribution/types', () => ({ isCloud: false }))
+
 describe('useSystemStatsStore', () => {
   let store: ReturnType<typeof useSystemStatsStore>