Add APP_EMAIL_ALLOWLIST gate on account creation

An optional comma-separated list of glob patterns restricting which
addresses may register, applied on top of APP_ALLOW_REGISTRATION. A
non-matching new address is silently ignored exactly like registration
being off; an address that already has an account can still sign in.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Support/Config.php

@@ -17,6 +17,8 @@ final class Config
         public readonly bool $displayErrors,
         /** When false, POST /auth/magic-link only signs existing users in -- it never creates a new account. */
         public readonly bool $allowRegistration,
+        /** Optional glob-pattern gate on which addresses may create an account. Empty => no restriction. */
+        public readonly EmailAllowlist $emailAllowlist,
         /** Base URL of the frontend, used to build magic links. */
         public readonly string $appUrl,
         /** WebAuthn relying party ID -- the domain a passkey is bound to. */
@@ -51,6 +53,7 @@ final class Config
         $jwtTtl = (int) (self::env('JWT_TTL') ?? '86400');
         $displayErrors = filter_var(self::env('APP_DEBUG', 'false'), FILTER_VALIDATE_BOOL);
         $allowRegistration = filter_var(self::env('APP_ALLOW_REGISTRATION', 'true'), FILTER_VALIDATE_BOOL);
+        $emailAllowlist = EmailAllowlist::fromString(self::env('APP_EMAIL_ALLOWLIST'));
 
         $appUrl = rtrim(self::env('APP_URL', 'http://localhost:5173'), '/');
 
@@ -86,6 +89,7 @@ final class Config
             $jwtTtl,
             $displayErrors,
             $allowRegistration,
+            $emailAllowlist,
             $appUrl,
             $webauthnRpId,
             $webauthnRpName,