coupons cannot have 0 or negative numbers anymore.

Fixes #16 (closed) and #20 (closed)

configure some shop_location fields to be numbers not text to get free frontend validation

modified:   templates/shop_location_form.j2
modified:   views/coupon.py

Summary by CodeRabbit

• New Features

  • Enhanced shop location form to handle both creation and editing of locations.
  • Updated coupon creation form with advanced validation and error checks.

• Bug Fixes

  • Corrected input types for shipping rates to prevent invalid entries.
  • Fixed spelling errors in template files for better readability and consistency.

• Style

  • Updated label styles to bold text for better visibility.
  • Added red asterisks for required fields to improve form clarity.