feat(pos-app): add sandbox mode and CI flag

[ignaciosantise]

Summary

• Add opt-in sandbox mode for POS payment testing without merchant credentials or a wallet.
• Simulate $0.01 success and $0.02 decline, with local transaction samples and sandbox banners.
• Disable merchant credential editing while sandbox mode is active.
• Add a sandbox-enabled checkbox to the Mobile POS release workflow and inject it into Android/iOS Expo builds.
• Keep production builds explicitly controllable for Apple review.

Validation

• YAML parsing passed for all three modified workflows.
• git diff --check passed.
• Prettier checks were run; the workflow files have existing formatting differences.
• Dependency-based lint/typecheck/tests could not run because node_modules is not installed in the workspace.

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Project	Deployment	Actions	Updated (UTC)
pos-demo	Ready	Preview	Aug 28, 2026 12:54pm
react-native-walletkit	Ready	Preview	Aug 28, 2026 12:54pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
react-native-appkit	Ignored	Preview	Aug 28, 2026 12:54pm

[claude]

Claude finished @ignaciosantise's task in 3m 38s —— View job

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Code Review

• Gather context
• Read changed files
• Run breaking changes subagent — ✅ No breaking changes found
• Run data classification subagent — ✅ No data classification issues found
• Post findings

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Found 3 issue(s)

Issue 1: Success/decline condition ($0.01 magic value) not surfaced to testers

ID: scan-sandbox-magic-amount-3f9a
File: dapps/pos-app/app/scan.tsx:231
Severity: MEDIUM
Category: code_quality

Context:

• Pattern: amountToCents(amount) === 1 decides whether sandbox payment succeeds or declines — 1 cent ($0.01) succeeds, every other amount declines
• Risk: Testers who enter any "natural" amount will always see a decline and may think the feature is broken; there is no in-app cue explaining the trigger rule
• Impact: Poor DX; friction during QA sessions; misleading test results
• Trigger: Any sandbox payment initiated with an amount other than $0.01

Recommendation: Document the rule in the sandbox banner or instruction text. Minimal change — update SandboxBanner or the instruction label on the scan screen:

// sandbox-banner.tsx or scan.tsx instruction text
"Sandbox mode · Enter $0.01 to approve, any other amount to decline"

Alternatively, make the threshold a named constant and document it in a comment.

Fix this →

---

Issue 2: "Copy payment link" copies a non-functional sandbox URL

ID: scan-sandbox-copy-url-a2c1
File: dapps/pos-app/app/scan.tsx:147
Severity: LOW
Category: code_quality

Context:

• Pattern: handleCopyPaymentUrl copies qrUri to clipboard; in sandbox mode qrUri is sandbox_${Date.now()}?amount=... — not a real payment URL
• Risk: A tester who taps the QR code copies a fake, unparseable string and may try to share/use it
• Impact: Confusing UX; misleading "Payment link copied" toast
• Trigger: Any tap on the QR code while sandbox mode is active

Recommendation: Disable the copy handler in sandbox mode or suppress the toast:

const handleCopyPaymentUrl = async () => {
  if (isSandboxPayment) return; // no real URL to copy
  await Clipboard.setStringAsync(qrUri);
  showSuccessToast("Payment link copied");
};

Fix this →

---

Issue 3: Missing accessibility label on SandboxBanner

ID: sandbox-banner-a11y-7d3e
File: dapps/pos-app/components/sandbox-banner.tsx:13
Severity: LOW
Category: code_quality

Context:

• Pattern: The banner View has no accessibilityRole or accessibilityLabel; screen readers will read only the raw text without announcing it as a status/alert region
• Risk: Low-vision users may not know they are in a non-production mode
• Impact: Accessibility gap for screen reader users
• Trigger: Any time the sandbox banner is visible

Recommendation:

<View
  accessibilityRole="alert"
  accessibilityLabel="Sandbox mode active. Payments are simulated."
  style={[styles.container, { backgroundColor: theme["bg-warning"] }, style]}
>

---

Breaking changes: ✅ None — store migration (v19→v20) initialises sandboxMode: false; workflow sandbox-enabled input defaults to false; all changes are additive behind the EXPO_PUBLIC_SANDBOX_ENABLED build-time flag.

Data classification: ✅ None — no real credentials or PII in sandbox data; secrets remain in secureStorage; CI workflows use ${{ secrets.* }} correctly.