Fix preview deployment OAuth redirect

- Add APP_URL to preview deployment secrets
- This ensures OAuth callback redirects to preview URL, not localhost

.github/workflows/fly-review.yml

···
           # Use smaller resources for review apps
           vmsize: shared-cpu-1x
           memory: 256
-          # Set OAUTH_REDIRECT_BASE dynamically for OAuth redirects
+          # Set OAUTH_REDIRECT_BASE and APP_URL dynamically for OAuth redirects
           secrets: |
-            OAUTH_REDIRECT_BASE=https://zzstoatzz-status-pr-${{ github.event.number }}.fly.dev
+            OAUTH_REDIRECT_BASE=https://zzstoatzz-status-pr-${{ github.event.number }}.fly.dev
+            APP_URL=https://zzstoatzz-status-pr-${{ github.event.number }}.fly.dev

fly.review.toml

···
   ENABLE_FIREHOSE = "true"
   DEV_MODE = "true"
   # OAUTH_REDIRECT_BASE will be set dynamically by the workflow
+  # APP_URL will be set dynamically by the workflow
 
 [http_service]
   internal_port = 8080