fix: amount precision, icon upload FormData error, and unsaved-edit guard

[darui3018823]

Summary

Three user-reported issues fixed, one commit each:

1. fix(form): reject amounts that exceed the safe integer range — Amounts above Number.MAX_SAFE_INTEGER were silently rounded by IEEE 754 doubles (e.g. 1145141919364364810 was stored as …800). The add/edit forms now validate against MAX_AMOUNT and show a dedicated error message (en/ja) instead of saving a corrupted value.

2. fix(upload): replace uri-based FormData part with expo-file-system File — Expo SDK 54+ replaces global fetch with its WinterCG implementation, which rejects React Native's legacy { uri, name, type } FormData parts with "Unsupported FormDataPart implementation", breaking icon upload after cropping. Uploads now append an expo-file-system File on native (Blob on web). Adds expo-file-system as a direct dependency (native module already bundled via the expo package, so no new native build is required); lockfile regenerated with pnpm 10 and verified with frozen installs on both pnpm 10 and 11.

3. feat(edit): confirm before discarding unsaved changes — Closing the edit screen via the × button / back gesture / swipe-down with unsaved edits now asks for confirmation (beforeRemove guard); saving skips the guard.

Test plan

• Enter an amount like 1145141919364364810 in add/edit → "amount too large" error, value not saved
• Edit screen → change icon → crop → ✓ → upload succeeds (no FormDataPart error)
• Edit screen → change any field → × → discard confirmation appears; "破棄" closes, "編集を続ける" stays
• Edit without changes → × closes immediately; saving closes without prompt

🤖 Generated with Claude Code

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Code Review

This pull request introduces several key improvements, including a validation check to reject subscription amounts exceeding the safe integer limit (MAX_AMOUNT) and a confirmation dialog in the edit screen to prevent users from accidentally discarding unsaved changes. Additionally, the file upload mechanism in lib/api.ts has been refactored to support both web and native platforms correctly using expo-file-system. The review feedback suggests optimizing the isDirty check in the edit form by using useMemo to cache the initial next payment date timestamp, which avoids redundant Date object instantiations on every keystroke.

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[darui3018823]

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Reviewed commit: 19d3b65baf

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[darui3018823]

@claude review

[claude]

Claude finished @darui3018823's task in 3m 44s —— View job

---

Review complete ✅

• Gather context (diff, changed files, existing review comments)
• Review app/add.tsx and app/edit.tsx amount validation logic (incl. Codex's fractional-rounding concern)
• Review lib/api.ts FormData/File upload change
• Review app/edit.tsx unsaved-changes guard (incl. Gemini's useMemo suggestion)
• Review lib/currency.ts, i18n changes, package.json/lockfile
• Post final review

Summary

Good news first: both prior automated review comments are already resolved by follow-up commits on this branch, not just left open:

• Codex's fractional-rounding concern (9007199254740991.1 slipping past the Number()-coerced comparison) was fixed in 1322177 — isAmountInputAboveMax (lib/currency.ts:39-60) now compares the raw integer-part string length/lexical order and checks for any nonzero trailing decimal digit, instead of relying on the rounded Number() value. I traced through the boundary cases (9007199254740991.1, ...990.9999, 20-digit overflow) and the logic holds up correctly in each.
• Gemini's useMemo suggestion for initialNextPaymentTimestamp was applied in 7815ede (app/edit.tsx:79-82).

Amount validation (app/add.tsx:61, app/edit.tsx:126)

Both forms now call isAmountInputAboveMax(amount) on the raw input string before parseAmountInput, so the check runs on the un-coerced value — this is the right order and avoids the original bug class entirely.

One very low-risk edge case I noticed but don't think is worth blocking on: isAmountInputAboveMax's decimal regex ^(\d+)(?:\.(\d*))?$ (lib/currency.ts:47) doesn't match a leading +/-, so an input like +9007199254740991.5 falls through to decimalMatch === null → returns false (not flagged as too large), even though parseAmountInput would go on to coerce/round it silently. Given the field uses keyboardType="numeric" this is hard to trigger from the on-screen keyboard, but a pasted value could hit it. Not asking for a change here, just flagging for awareness.

Upload fix (lib/api.ts:544-556)

The web/native split (Blob via fetch().blob() on web, expo-file-system File on native) matches the documented WinterCG fetch constraint, and the expo-file-system: ~57.0.0 pin is consistent with the other expo-* deps already on SDK 57. I couldn't install dependencies in this sandbox (no node_modules, no network) to actually exercise the upload path, so I'm relying on the PR description's manual test plan for the runtime behavior — worth double-checking the icon still renders correctly post-upload on both a fresh native build and web once merged, per your own checklist.

Unsaved-changes guard (app/edit.tsx:78-119)

Logic looks correct: beforeRemove guard checks isDirtyRef/skipDirtyGuardRef, and handleSave sets skipDirtyGuardRef.current = true before router.back() so saving never prompts. The modal is registered with presentation: 'modal' in app/_layout.tsx:99, so this also covers the swipe-down dismiss gesture as called out in the test plan.

Minor note (not a bug): billingCycle/paymentMethod/currency come from the shared useAddFormStore, which is populated from subscription in a separate useEffect (app/edit.tsx:72-76) rather than at useState init time. There's a theoretical one-render window where isDirty could read stale values left over from a previous add/edit session before that effect runs, but it's not practically reachable by a user action and pre-dates this PR's change.

Environment note

This sandbox has no network access and no node_modules installed, so I wasn't able to run pnpm lint/pnpm install/build to verify formatting or type-check the expo-file-system File usage — the diff reads correctly by inspection, but if CI hasn't run lint/typecheck yet on this branch it'd be worth confirming there.

Overall: this looks solid and ready to merge pending CI. Nice job addressing both bots' feedback proactively in follow-up commits.