fix(ci): add auth env vars to convex preview

Preview Convex deployments were missing:
- BETTER_AUTH_SECRET (required for oAuthProxy)
- GITHUB_CLIENT_ID
- GITHUB_CLIENT_SECRET

These are now set from GitHub secrets during deployment.

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

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

Author: leoisadev1

.github/workflows/preview-deploy.yml

@@ -61,18 +61,30 @@ jobs:
         working-directory: apps/server
         env:
           CONVEX_DEPLOY_KEY: ${{ secrets.CONVEX_PREVIEW_DEPLOY_KEY }}
+          BETTER_AUTH_SECRET: ${{ secrets.BETTER_AUTH_SECRET }}
+          GITHUB_CLIENT_ID: ${{ secrets.AUTH_GITHUB_CLIENT_ID }}
+          GITHUB_CLIENT_SECRET: ${{ secrets.AUTH_GITHUB_CLIENT_SECRET }}
         run: |
           echo "⚙️ Setting Convex environment variables..."
 
           PR_NUM=${{ github.event.pull_request.number }}
           RAILWAY_URL="https://web-openchat-pr-${PR_NUM}.up.railway.app"
 
+          # Core settings
           bunx convex env set SITE_URL "$RAILWAY_URL" --preview-name pr-${PR_NUM}
           bunx convex env set NEXT_PUBLIC_DEPLOYMENT "preview" --preview-name pr-${PR_NUM}
 
+          # Auth settings - must match production for oAuthProxy to work
+          bunx convex env set BETTER_AUTH_SECRET "$BETTER_AUTH_SECRET" --preview-name pr-${PR_NUM}
+          bunx convex env set GITHUB_CLIENT_ID "$GITHUB_CLIENT_ID" --preview-name pr-${PR_NUM}
+          bunx convex env set GITHUB_CLIENT_SECRET "$GITHUB_CLIENT_SECRET" --preview-name pr-${PR_NUM}
+
           echo "✅ Convex env vars set"
           echo "   SITE_URL: $RAILWAY_URL"
           echo "   NEXT_PUBLIC_DEPLOYMENT: preview"
+          echo "   BETTER_AUTH_SECRET: [set]"
+          echo "   GITHUB_CLIENT_ID: [set]"
+          echo "   GITHUB_CLIENT_SECRET: [set]"
 
       - name: Configure Railway Environment
         env: