Onboarding: link to provider signup/key pages (and optionally guided browser-based registration)

Problem

Today, onboarding a new provider is a fully manual loop: the user has to find each provider's signup page in a browser, register (usually just Google/GitHub OAuth), generate an API key, and paste it into the dashboard Keys page. Nothing in FreeLLMAPI helps discover or even link to the right signup/console URL.

Proposal (two levels)

Level 1 — minimum: the server/dashboard should know each supported platform's signup + API-key-console URLs and offer a direct link ("Get a key →") next to every provider on the Keys page, and/or the CLI should print them (e.g. freellmapi setup-keys or as part of doctor).

Level 2 — nice to have: semi-automated registration via a local browser-automation agent (e.g. browser-use or Playwright-driven flow): open the provider's signup page, pre-fill what it can, and hand control back to the user at the OAuth/captcha/verification step. Full unattended registration is out of scope on purpose — it would violate most providers' ToS and trip captchas anyway. A guided "open the page, I'll take it from here when you've logged in" flow would remove most of the friction while staying compliant.

Why

Registration across ~16 providers is the single biggest one-time friction of the project. Even Level 1 (correct links) is cheap and helps a lot; Level 2 makes onboarding nearly turnkey.