fix(auth): surface email-not-verified error and detect needsVerification on signup

- mana-auth login route: catch Better Auth's email verification error and
  return 403 EMAIL_NOT_VERIFIED instead of 401 Invalid credentials
- shared-auth signUp: detect emailVerified:false in register response and
  return needsVerification:true so the UI shows the verification prompt
- shared-auth-ui LoginPage: map INVALID_CREDENTIALS error code to friendly message
- shared-i18n: add invalidCredentials translation (de/en)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/shared-i18n/src/translations/auth/de.json

@@ -19,6 +19,7 @@
 		"emailInvalid": "Bitte gib eine gültige E-Mail-Adresse ein",
 		"passwordRequired": "Passwort ist erforderlich",
 		"signInFailed": "Anmeldung fehlgeschlagen",
+		"invalidCredentials": "Ungültige E-Mail oder Passwort",
 		"signInSuccess": "Erfolgreich angemeldet. Weiterleitung...",
 		"emailVerified": "E-Mail erfolgreich bestätigt! Bitte melde dich an.",
 		"emailNotVerified": "E-Mail nicht bestätigt.",

packages/shared-i18n/src/translations/auth/en.json

@@ -19,6 +19,7 @@
 		"emailInvalid": "Please enter a valid email address",
 		"passwordRequired": "Password is required",
 		"signInFailed": "Sign in failed",
+		"invalidCredentials": "Invalid email or password",
 		"signInSuccess": "Successfully signed in. Redirecting...",
 		"emailVerified": "Email successfully verified! Please sign in.",
 		"emailNotVerified": "Email not verified.",

packages/shared-i18n/src/translations/auth/index.ts

@@ -34,6 +34,7 @@ export interface AuthTranslations {
 		emailInvalid: string;
 		passwordRequired: string;
 		signInFailed: string;
+		invalidCredentials?: string;
 		signInSuccess: string;
 		emailVerified?: string;
 		emailNotVerified?: string;