Phase 5: Translate Auth Pages - login and signup

- Create auth.json translation files for es, en, ca
- Translate login page: title, subtitle, form labels, buttons, footer
- Translate signup page: invite code step and account creation step
- Translate signup/[code] redirect page
- Update IntlProvider to load auth namespace
- Update test expectations to match Spanish translations (default language)
- All frontend and e2e tests passing

frontend/locales/en/auth.json

@@ -0,0 +1,44 @@
+{
+  "login": {
+    "title": "Welcome back",
+    "subtitle": "Sign in to your account",
+    "email": "Email",
+    "password": "Password",
+    "emailPlaceholder": "you@example.com",
+    "passwordPlaceholder": "••••••••",
+    "signIn": "Sign in",
+    "signingIn": "Signing in...",
+    "noAccount": "Don't have an account?",
+    "signUp": "Sign up",
+    "loginFailed": "Login failed"
+  },
+  "signup": {
+    "title": "Join with Invite",
+    "subtitle": "Enter your invite code to get started",
+    "inviteCode": "Invite Code",
+    "inviteCodePlaceholder": "word-word-00",
+    "inviteHint": "Ask your inviter for this code",
+    "checking": "Checking...",
+    "continue": "Continue",
+    "checkingInviteCode": "Checking invite code...",
+    "createAccount": "Create account",
+    "createAccountTitle": "Create account",
+    "createAccountSubtitle": "Using invite:",
+    "email": "Email",
+    "emailPlaceholder": "you@example.com",
+    "password": "Password",
+    "passwordPlaceholder": "••••••••",
+    "confirmPassword": "Confirm Password",
+    "confirmPasswordPlaceholder": "••••••••",
+    "creatingAccount": "Creating account...",
+    "alreadyHaveAccount": "Already have an account?",
+    "signIn": "Sign in",
+    "useDifferentCode": "Use a different invite code",
+    "redirecting": "Redirecting...",
+    "passwordsDoNotMatch": "Passwords do not match",
+    "passwordTooShort": "Password must be at least 6 characters",
+    "invalidInviteCode": "Invalid invite code",
+    "failedToVerify": "Failed to verify invite code",
+    "registrationFailed": "Registration failed"
+  }
+}