binarybeachio: repurpose GitHub OAuth as Zitadel OIDC

Patches the plane-backend GitHubOAuthProvider so the /auth/github/*
flow points at our self-hosted Zitadel instance when ZITADEL_DOMAIN
is set, and falls back to vanilla GitHub OAuth when unset (regression-
safe). Touch surface is one backend file plus a cosmetic frontend
label change. Full rationale, configuration steps, refresh procedure,
and AGPL compliance notes in BINARYBEACHIO.md at repo root.

apps/web/core/hooks/oauth/core.tsx

@@ -46,14 +46,18 @@ export const useCoreOAuthConfig = (oauthActionText: string): TOAuthConfigs => {
       enabled: config?.is_google_enabled,
     },
     {
+      // binarybeachio fork — this OAuth slot is repurposed as our Zitadel SSO
+      // entry point (the backend's GitHubOAuthProvider was patched to point at
+      // Zitadel — see provider/oauth/github.py). Branding is rebranded here;
+      // backend identifiers (route, env vars, DB provider key) stay "github".
       id: "github",
-      text: `${oauthActionText} with GitHub`,
+      text: `${oauthActionText} with binarybeach.io`,
       icon: (
         <img
           src={resolvedTheme === "dark" ? GithubDarkLogo : GithubLightLogo}
           height={18}
           width={18}
-          alt="GitHub Logo"
+          alt="binarybeach.io SSO"
         />
       ),
       onClick: () => {