refactor: extract quickpay repository

[ovitrif]

Goal

Extract a QuickPayRepo (or similarly named repository) for QuickPay policy + daily spend ledger concerns that are currently spread across AppViewModel, QuickPayViewModel, and CacheStore, so call sites only delegate instead of re-implementing conversion/cap math.

Why this was deferred from #1159

#1159 is a security-facing QuickPay daily spend limit patch. The daily-cap work added enough shared logic that a repository extraction is justified, but applying that refactor in the same PR would:

• Expand review surface beyond the security fix
• Mix behavioral change with structural move
• Slow shipping the patch

Rationale: Keep #1159 limited to the security fix; do this extraction after it is merged.

Scope

In scope

• Daily-cap resolution (settings threshold × multiplier, USD conversion)
• Spent-today / reserve / release ledger APIs (currently on CacheStore, orchestrated from VMs)
• Eligibility: “can this amount use QuickPay?” used by AppViewModel gating and consistent with pay-time checks
• ViewModels delegate to the repo; keep UI state and navigation in VMs
• Android journeys for daily-cap behavior (see below)

Out of scope

• Moving payInvoice / node event watching out of LightningRepo
• Reworking QuickPay settings UI
• Changing product rules for the daily limit (behavior should stay equivalent to post-fix: add quickpay daily spend limit #1159)

Journeys

Add journeys/quickpay/ (README + XML), patterned after journeys/amount-limits/.

Setup: funded spending balance via bitkit-docker / LSP; QuickPay enabled.

Cover:

1. Under per-tx + daily cap → QuickPay path (no Confirm / payment PIN)
2. Over / exhausted daily cap → Confirm path

Acceptance criteria

• Implementation work starts on master after fix: add quickpay daily spend limit #1159 is merged
• Shared QuickPay policy + spend ledger live behind a repository API returning Result / simple types as appropriate
• AppViewModel and QuickPayViewModel no longer duplicate daily-cap / USD conversion math
• Existing unit coverage for spend reserve/release and QuickPay gating is updated/moved with the extraction
• Unit tests are added for the new repository covering its logic
• journeys/quickpay/ documents setup and covers under-cap QuickPay + over-cap Confirm
• just compile, targeted unit tests, and just lint pass

References

• PR: fix: add quickpay daily spend limit #1159