openai/gpt-chat-latest → B (3:1)

Side B centralizes base URL generation into a shared utility, replaces multiple hardcoded environment/hostname checks across OAuth, login, and callback code with that utility, uses the browser origin when available, and updates deployment to staging, improving configurability for custom hosts. Side A is a focused correctness fix that skips stickied/pinned Reddit posts during import and adds a targeted regression test, but it affects a narrower part of the system.