feat(topup): show net "you'll receive" and enforce $10 minimum on card top-ups

[islandbitcoin]

What & why

Fast-follow to the merged backend fee feature (lnflash/flash#473), which added a nullable Globals.fygaroTopup field carrying the Fygaro processor + Flash fee params and the top-up minimum. This wires the app to consume them so a card top-up is transparent about fees and enforces a real minimum.

Two user-facing changes on the card top-up amount screen (TopupDetails, paymentType: "card"):

1. Fee disclosure — "You'll receive $X.XX" (net after fees) is shown live as the user types, computed client-side from the fee params. Reuses the visual/interaction pattern of the cashout settlement-amount preview shipped in feat(cashout): show the real settlement amount on the cashout entry screen #683.
2. $10 minimum — the old >= $1.00 card check is replaced with fygaroTopup.minimumAmount, and the invalid-amount alert now states the real minimum.

Net is computed as:

processorFee = gross * processorFeePercent/100 + processorFeeFixed
flashFee     = gross * flashFeePercent/100     + flashFeeFixed
net          = max(0, gross - processorFee - flashFee)

e.g. $10 gross with 2.99% + $0.49 processor and 2% flash → $9.01.

Null-degradation

fygaroTopup is null when the instance's Fygaro settings are unavailable. The app handles that gracefully:

• the "You'll receive" line is hidden (never shows a guessed/wrong number), and
• the minimum falls back to $10 rather than silently dropping to the old $1.

Both are card-only — bank-transfer / bridge flows keep the existing $1 floor and show no net line.

GraphQL field consumed

Added fygaroTopup { minimumAmount processorFeePercent processorFeeFixed flashFeePercent flashFeeFixed } to the existing transferFlags globals query (the one that already surfaces bridgeEnabled, fetched by the topup/cashout entry screen — so the data is cache-warm on arrival to TopupDetails).

Since this worktree has no backend access to re-introspect, the FygaroTopupInfo type and the fygaroTopup: FygaroTopupInfo field were hand-added to the committed app/graphql/public-schema.graphql to match flash#473, then codegen was regenerated (yarn dev:codegen) — generated.ts / generated.gql are in the diff. graphql-inspector validates clean.

i18n

New keys (TopupDetails.youllReceive, TopupDetails.feeNote, and a parameterized TopupDetails.minimumAmount) added to app/i18n/en/index.ts and to all 23 locale files under raw-i18n/translations/ (English placeholder, per convention). yarn update-translations and check:translation-drift both clean.

Tests

app/screens/topup-cashout-flow/__tests__/TopupDetails.test.tsx extended (globals hook mocked the way CardPayment mocks its query hook):

• $5 card amount is rejected with the real-minimum alert (incl. the null-fallback path)
• $10 gross renders "You'll receive $9.01"
• net line hidden when fygaroTopup is null and for bank transfers
• pure estimateTopupNet unit tests (sample + negative clamp)

yarn check-code (tsc + translations + codegen + graphql-check) passes; yarn test for the flow is green (23/23).

🤖 Generated with Claude Code

https://claude.ai/code/session_01NcEjF6SS3Ci5D4CzZqdPjb