Sign-in lands on a Keycloak page branded "Minecraft Cities Network | Economy Explorer"; remove the interstitial and add social login

Part of PAR-357. Marked urgent because this is the first thing every new user sees.

Problem (seen live)

1. An extra interstitial. app.taskl.ie/login shows an unbranded card ("Sign in to taskl.ie", an explanatory paragraph, "Continue to sign in", and a hedge: "Account creation and password recovery, when available, are on the next screen. Use the username your workspace owner added.") (ui/app/login/page.tsx:16-44). There's no logo. It's one more click before the real form.
2. Wrong button label. Clicking "Continue to sign in" changes it to "Saving…", and the layout shifts.
3. Wrong product branding. The Keycloak page that follows (auth.paradaux.io, realm minecraft) is titled "Minecraft Cities Network | Economy Explorer" with a purple Economy Explorer theme. It asks for "Username" (not email) and offers "New user? Register". A taskl.ie user lands in a different product.
4. No social sign-in or magic link, and no forgot-password link on the visible form.

Reference

• Firecrawl: logo, Log in / Sign up tabs, email + password, "Sign in via magic link", Continue with GitHub/Google/SSO (Mobbin).
• Peec AI: a split layout with social proof (Mobbin).
• Twingate: workspace-branded SSO buttons (Mobbin).

Do

• Give taskl.ie its own Keycloak client/realm theme (taskl.ie logo, sage brand, warm background), or a dedicated realm. Never show Economy Explorer branding.
• Skip the interstitial: /login redirects straight to the IdP (keep the card only as an error fallback), or render the branded form ourselves.
• Add identity providers: Discord (the product is Discord-first), GitHub and Google. Use email as the login, with magic-link or passwordless as an option.
• Fix the pending label ("Redirecting…") and the layout shift.