Add reusable two-factor verification for login and money operations (#32)

frontend/app/lib/l10n/en.arb

@@ -227,5 +227,40 @@
   "wLimitsScope": "Outgoing activity · EUR equivalent",
   "wPendingHint": "Refresh to check the latest status. You can keep using your other accounts.",
   "wFundsHeading": "Where is my money?",
-  "wAnother": "Make another transaction"
+  "wAnother": "Make another transaction",
+  "factorTitle": "One more check.",
+  "factorLogin": "Confirm it’s you to finish signing in.",
+  "factorMoney": "Confirm this transaction. No money moves before confirmation.",
+  "factorEnableHelp": "Confirm to turn on two-factor verification for sign-in and money operations.",
+  "factorDisableHelp": "Confirm to turn off two-factor verification. Sign-in and money operations will no longer ask for a second code.",
+  "factorEmail": "Enter the six-digit code sent to your email.",
+  "factorAuthenticator": "Enter the current six-digit code from your authenticator app.",
+  "factorCode": "Verification code",
+  "factorConfirm": "Verify and continue",
+  "factorResend": "Send a new code",
+  "factorHelp": "Check your inbox and spam folder. A new code replaces the previous one.",
+  "factorAppHelp": "Use the current code. If you cannot access your authenticator, cancel this action.",
+  "factorInvalid": "That code is not valid. Check all six digits and try again.",
+  "factorExpired": "This verification has expired. Request a new code or return to start again.",
+  "factorLocked": "Too many incorrect attempts. Wait five minutes, then start verification again.",
+  "factorWait": "Please wait before requesting another code.",
+  "factorRequired": "Verification is needed again. Please confirm this action once more.",
+  "factorUnavailable": "Could not complete verification. Try again or cancel this action.",
+  "factorCooldown": "Send a new code in {seconds}s",
+  "factorSettings": "Two-factor verification",
+  "factorSettingsHelp": "Add a verification code when you sign in, top up, exchange or pay out.",
+  "factorOn": "On",
+  "factorOff": "Off",
+  "factorEnable": "Turn on",
+  "factorDisable": "Turn off",
+  "@factorCooldown": {
+    "placeholders": {
+      "seconds": {
+        "type": "int"
+      }
+    }
+  },
+  "factorEmailMethod": "Email code",
+  "factorAppMethod": "Authenticator app",
+  "factorAppExpired": "This verification has expired. Return and start again."
 }