Enforce integer-only values for rent amount field

- Add .int() validation to rentAmount in FormSchema
- Remove decimal formatting (was dividing by 100)
- Change min value from 0 to 1
- Add right text alignment for better numeric display
- Add localization for integer validation error message

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

messages/en.json

@@ -164,6 +164,7 @@
       "tenant-email-required": "tenant email is missing",
       "tenant-email-invalid": "email address is invalid",
       "rent-amount-required": "rent amount is required when rent notification is enabled",
+      "rent-amount-integer": "rent amount must be a whole number (no decimal places)",
       "rent-amount-positive": "rent amount must be a positive number",
       "validation-failed": "Validation failed. Please check the form and try again."
     }