Every /v1 mutating route that previously accepted role=="api" without
permission checks now uses requireRoleOrAPIPermission — JWT human roles OR
API keys that carry the concrete permission. R2-3 regression surface:
- /v1/transactions → mpc:transactions:create
- /v1/subscriptions/* → mpc:subscriptions:write
- /v1/payment-requests/* → mpc:payment-requests:write
- /v1/smart-wallets/* → mpc:smart-wallets:write
- /v1/trade/* → mpc:trade:write
- /v1/intents/* (sign/co-sign) → mpc:sign (same perm as /v1/mpc/sign)
- /v1/mpc/operations/approve,reject → mpc:operations:approve
Bare role=="api" is no longer sufficient anywhere — an API key with empty
permissions hits 403. Human roles (owner/admin/signer) still pass through
on JWT auth. Also adds the canonical requireRoleOrAPIPermission helper to
middleware.go.