Remove dead Stripe Checkout v1 code and gem

[mroderick]

Stripe Checkout v1 was sunset by Stripe in 2022. The payments#new form view was deleted in July 2022 (commit f25f10b8), leaving the controller, JS, Stripe initialiser, route, and tests as unreachable dead code.

The donation page (/donate) only links to external platforms (Enthuse, Open Collective, GitHub Sponsors, etc.) — there is no inline payment flow.

Removed

• app/assets/javascripts/payments.js — StripeCheckout.configure() handler
• app/controllers/payments_controller.rb
• app/views/payments/create.html.haml
• spec/controllers/payments_controller_spec.rb
• config/initializers/stripe.rb
• stripe gem from Gemfile

Updated

• config/routes.rb — removed resources :payments
• config/initializers/assets.rb — removed payments.js precompile

Verification

• Controller specs: 153 examples, 0 failures
• Model specs: 335 examples, 0 failures
• Feature specs: 302 examples, 0 failures

[olleolleolle]

Amazing cleanup!