refactor: update MainForm layout and payment method selection; localize submit button text

frontend/src/utils/i18n/locales/en/en.json

@@ -7,7 +7,7 @@
     "street": "Street + House No.",
     "postal-code": "Postal Code + City",
     "email": "Email",
-    "submit": "Buy",
+    "submit": "Submit Form",
     "failed-to-load-users": "Failed to load users.",
     "user": "User",
     "next-id": "Next Entry Number: ",
@@ -20,8 +20,8 @@
     "transfer": "Other (note down)",
     "ticket-payment_one": "You have successfully purchased {{count}} ticket.",
     "ticket-payment_other": "You have successfully purchased {{count}} tickets.",
-    "ticket": "ticket",
-    "tickets": "tickets",
+    "ticket": "Ticket",
+    "tickets": "Tickets",
     "entry-id": "Entry ID",
     "thank-you": "Thank you for supporting the Claudius Akademie! We wish you the best of luck with your ticket.",
     "select-payment-method": "Select Payment Method"