Revert "Allow private-network CORS origins in development"

This reverts commit 1b2e0cb8af.

.env.example

@@ -36,7 +36,6 @@ PROVIDER_BASE_URL_ALLOWLIST=[]
 PUBLIC_BASE_URL=http://localhost:8000
 CORS_ORIGINS=["http://localhost:5173","http://localhost:3000"]
 CORS_ALLOW_CREDENTIALS=false
-CORS_ALLOW_DEVELOPMENT_PRIVATE_NETWORK_ORIGINS=true
 VITE_API_BASE=
 
 # Production baseline overrides (set explicitly for live deployments):
@@ -51,5 +50,4 @@ VITE_API_BASE=
 # PUBLIC_BASE_URL=https://api.example.com
 # CORS_ORIGINS=["https://app.example.com"]
 # CORS_ALLOW_CREDENTIALS=false
-# CORS_ALLOW_DEVELOPMENT_PRIVATE_NETWORK_ORIGINS=false
 # VITE_API_BASE=https://api.example.com/api/v1