feat: add preview version badge for nightly builds (#8222)

## Summary

Adds a "Preview Version" badge to the topbar on nightly builds to help
users identify when they're using an unreleased version and encourage
feedback.

## Changes

- Add `nightly.badge` i18n translations (label and tooltip)
- Create `nightlyBadges.ts` extension with info variant badge
- Load nightly badges extension when `isNightly` is true
- Badge tooltip encourages users to provide feedback via the feedback
button

## Test plan

- [ ] Build and run nightly version, verify "NIGHTLY | Preview Version"
badge appears in topbar
- [ ] Hover over badge, verify tooltip shows: "You are using a nightly
version of ComfyUI. Please use the feedback button to share your
thoughts about these features."
- [ ] Verify stable OSS builds don't show the badge
- [ ] Verify cloud builds don't show the nightly badge

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8222-feat-add-preview-version-badge-for-nightly-builds-2ef6d73d36508102aa0dfc22ef14c9c1)
by [Unito](https://www.unito.io)

src/locales/en/main.json

@@ -275,6 +275,7 @@
     "1x": "1x",
     "2x": "2x",
     "beta": "BETA",
+    "nightly": "NIGHTLY",
     "profile": "Profile",
     "noItems": "No items"
   },
@@ -2634,5 +2635,11 @@
       "workspaceNotFound": "Workspace not found",
       "tokenExchangeFailed": "Failed to authenticate with workspace: {error}"
     }
+  },
+  "nightly": {
+    "badge": {
+      "label": "Preview Version",
+      "tooltip": "You are using a nightly version of ComfyUI. Please use the feedback button to share your thoughts about these features."
+    }
   }
 }