Remove leftover Firebase build-args from Docker workflow

App no longer uses Firebase — these were vestigial from an earlier version.
The exposed API key should be rotated in the Firebase console.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/docker.yml

@@ -44,11 +44,3 @@ jobs:
         push: true
         tags: ${{ steps.meta.outputs.tags }}
         labels: ${{ steps.meta.outputs.labels }}
-        build-args: |
-          NEXT_PUBLIC_FIREBASE_API_KEY=AIzaSyAYZFoBQmi1PXPtHXOZy5agUBlt-WdrEM8
-          NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN=budget-dee6c.firebaseapp.com
-          NEXT_PUBLIC_FIREBASE_PROJECT_ID=budget-dee6c
-          NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET=budget-dee6c.appspot.com
-          NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID=1084588982613
-          NEXT_PUBLIC_FIREBASE_APP_ID=1:1084588982613:web:df0c08f99b2f238ca96fdc
-          NEXT_PUBLIC_ENCRYPTION_KEY=CHANGE_THIS_TO_A_SECURE_ENCRYPTION_KEY