Integrate email notifications into signup and login (#38)

frontend/app/lib/l10n/en.arb

@@ -43,10 +43,11 @@
   "authCompleted": "Request completed.",
   "authInvalidCredentials": "Email or password is incorrect. Please try again.",
   "authEmailInUse": "This email is already registered. Try logging in.",
+  "authVerifyEmail": "Confirm your email before signing in.",
   "authUnavailable": "The service is unavailable. Please try again.",
   "authUnexpected": "Something went wrong. Please try again.",
   "checkInbox": "Check your inbox.",
-  "verificationSent": "We’ve sent you a verification email. Open the link in your inbox to confirm your email address.",
+  "verificationSent": "If this email belongs to an unverified account, a verification email is on its way. Open the link in your inbox to confirm your address.",
   "verificationSending": "Preparing your verification email…",
   "verificationChecking": "Verifying your email…",
   "verificationVerified": "Your email\nis verified.",