Prod: public origin gupi.glitch.university, internal services over HTTP

CORS_ORIGIN defaults to https://gupi.${DOMAIN} (the TLS frontend served by the
proxy); the app still reaches Postgres/MinIO by their docker hostnames over
plain HTTP on the shared network. Clarify the split in .env.prod.example and
fix the deploy success URL.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -1,6 +1,9 @@
 node_modules/
 dist/
 .env
+.env.prod
+.env.local
+.env.*.local
 .DS_Store
 *.tsbuildinfo
 playwright-report/