Add Auth0 environment variables to build step

VITE_AUTH0_CLIENTID and VITE_AUTH0_DOMAIN are needed at build time
as they get embedded into the frontend bundle by Vite.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -24,6 +24,8 @@ jobs:
         timeout-minutes: 10
         env:
           NODE_OPTIONS: '--max-old-space-size=4096'
+          VITE_AUTH0_CLIENTID: ${{ secrets.VITE_AUTH0_CLIENTID }}
+          VITE_AUTH0_DOMAIN: ${{ secrets.VITE_AUTH0_DOMAIN }}
 
       - name: Stop Service
         run: |