feat: add Paykit subscriptions

[ben-kaufman]

Description

Adds the payer side of Paykit subscriptions, stacked on #1199, which is stacked on #1178.

• Receives private subscription proposals and lets the payer review and confirm them.
• Requires an immediately due first period to be paid before showing the subscribed success state; failed or uncertain payments remain due and can be retried.
• Turns each unpaid billing period into the existing incoming payment-request flow, including automatic presentation, the bell queue, and the Payments tab.
• Schedules local due-payment notifications and opens the corresponding request when the notification is selected.
• Adds the Figma-aligned Subscriptions and Payments tabs, subscription detail/status views, cancellation, empty states, and fixed/open-ended summaries.
• Shows a normalized Monthly Cost across all active subscriptions, independent of whether the current periods are already paid.
• Associates payment proofs with their exact billing period so recurring periods remain independent while retaining private-only resolution and fresh Private Payment List requirements.
• Keeps subscribe-and-pay inside one continuously presented sheet, including initial-payment failure and retry, without the modal dismissal/reappearance gap.
• Retains the settled payment rail in completed request and subscription history so Lightning feedback is purple and on-chain feedback is orange, including success confetti.

This PR intentionally covers payer-side receipt only. Subscription creation, Discover, automatic payment without confirmation, and renewal are not included because they are outside this MVP or are not currently exposed by Paykit.

Dependencies:

• Paykit 0.1.0-rc46
• Hardware-wallet payment proofs #1199
• Payment proof delivery #1178
• iOS companion PR #685

Preview

Final Android and cross-platform proof recordings were completed locally; they are not attached to the PR.

QA Notes

Manual Tests

• Receive an immediate-start private subscription proposal and verify review → payment → success stays in one continuously presented sheet.
• Exercise initial-payment failure and retry and verify the Send sheet remains presented while the first period stays due.
• Verify Lightning and on-chain subscription success choose purple/orange confetti and matching completed-payment icons.
• Receive a future-start proposal, trigger its due notification, and open the exact billing-period payment.
• Dismiss and reopen a due request from the bell queue and Payments tab, then pay it with fresh private payment details.
• Review active, expired, fixed-term, and open-ended subscription details and cancel an active subscription.

Automated Checks

• Full testDevDebugUnitTest suite
• Focused PaykitPaymentRequestRepoTest, PaykitPaymentRequestRepoSubscriptionTest, SubscriptionsScreenTest, and AppViewModelSendFlowTest
• compileDevDebugKotlin
• compileDevDebugAndroidTestKotlin
• detekt --rerun-tasks
• arm64 assembleDevDebug, install, and cold launch on API 36 emulator CodexBullTlsUiApi36
• git diff --check

[jvsena42]

could test the PR stack feature for this case

[ben-kaufman]

Done: the PR now uses the stack directly. #1186 is based on the hardware-proof fix #1199, which is based on #1178, so each review contains only its own layer.

[jvsena42]

Duplicated component

[ben-kaufman]

@jvsena42 Fixed in dd53772. The duplicated fiat value came from replacing the subscription review sheet while its content was still composed. The flow now reuses the existing dismiss-delay-present sheet transition and waits for that transition before validating the destination. The focused send-flow regression passes.

[ben-kaufman]

The duplicated subscription payment UI is fixed in signed commit dd53772. The review sheet now completes its normal dismiss transition before the Send sheet is presented, and the focused send-flow regression covers the sequence. @jvsena42 please re-review the updated head when E2E finishes.

[ovitrif]

prepareHardwareContactPayment marks the on-chain proof started before the hardware device signs, but onHardwareSignCancelled and send-sheet dismiss never call failOnchainPayment. The due request then stays in inFlightRequestIds and a later prepare() fails with OperationInProgress.

Also:

• Several new Kotlin sites still use inline fully-qualified names where an import would do.
• wallet__payment_request_timestamp is unused after paymentRequestDateTime was removed.

[ovitrif]

utACK

The base branch was changed.

[ben-kaufman]

Updated per the Figma clarification: the overview now shows a normalized Monthly Cost across all active subscriptions, independent of whether their current periods are paid. Daily, weekly, monthly, and yearly recurrences are annualized to a monthly value; each subscription is rounded to the nearest satoshi before safe aggregation. The obsolete calendar-month refresh was removed, and regression coverage includes recurrence normalization, paid active subscriptions, inactive exclusions, and low-value rounding.

[ovitrif]

Could not drive the six Manual Tests on this head. Two emulators onboarded with Paykit enabled and paired as contacts, but Bitkit has no create-subscription path, so SubscriptionsScreen stayed empty.

QA Notes

Pixel_8_Pro emulator-5554 and Pixel_10_Pro_XL emulator-5556 (dev/regtest). Onboarding, the Paykit toggle, the Subscriptions empty state, and mutual pubky pairing worked. Immediate-start, retry, confetti, future-start notification, bell-queue, and cancel were not exercised.