fix(auth): stop wiki login loop to coming-soon and surface non-member state

Members (and pre-registrants) hitting wiki.ghostguild.org were getting bounced
to /coming-soon with a "Pre-Register" link, even when the OIDC flow was
working correctly.

- Allowlist /auth/oidc-error, /auth/logout-confirm, /auth/logout-success,
  and /verify in the coming-soon middleware so OIDC errors and main-site
  magic links stop redirecting to the pre-register page.
- Raise OIDC Interaction TTL from 10m to 15m so it outlives the magic-link
  JWT and legitimate members don't hit expired-interaction errors when they
  click the email a few minutes late.
- Differentiate the "email isn't a registered member" response on the wiki
  login route and show a dedicated "Not a member yet" state with a
  pre-register link and contact email, instead of the misleading
  "Check your inbox" that silently failed.

server/utils/oidc-provider.ts

@@ -81,7 +81,7 @@ export async function getOidcProvider() {
       AuthorizationCode: 600, // 10 minutes
       RefreshToken: 14 * 24 * 60 * 60, // 14 days
       Session: 14 * 24 * 60 * 60, // 14 days
-      Interaction: 600, // 10 minutes
+      Interaction: 900, // 15 minutes — must match magic-link JWT TTL so the interaction outlives the token
       Grant: 14 * 24 * 60 * 60, // 14 days
     },