PaymentService construction now initializes crypto master keys, so the tests
need a real migrated SQLite DB rather than a Mock. Also align with the current
code: initiate_topup delegates to create_topup_intent/create_topup_order; the
Stripe webhook path requires amount in metadata, passes a metadata dict, and is
exercised by patching stripe.Webhook.construct_event; crypto deposits credit the
fiat wallet directly via SQL (assert the resulting balance) using the monitor's
own price service (returning a float for SQLite binding).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>