switch prod arroba env vars to point to ATProto federation sandbox

https://atproto.com/blog/federation-developer-sandbox

app.yaml

@@ -22,9 +22,17 @@ inbound_services:
 - warmup
 
 env_variables:
-  PLC_HOST: plc.directory
-  APPVIEW_HOST: api.bsky.app
-  BGS_HOST: bgs.bsky.social
+  PDS_HOST: fed.brid.gy
+
+  # sandbox
+  PLC_HOST: plc.bsky-sandbox.dev
+  APPVIEW_HOST: api.bsky-sandbox.dev
+  BGS_HOST: bgs.bsky-sandbox.dev
+
+  # prod
+  # PLC_HOST: plc.directory
+  # APPVIEW_HOST: api.bsky.app
+  # BGS_HOST: bgs.bsky.social
 
 handlers: