feat(scan): on-device receipt parser, OCR fixes and a review screen

[Ivan-LB]

Summary

• Spike first: docs/spikes/receipt-scan-spike.md — what the scanner does today (with the extraction code run verbatim on fixtures), how the industry does it (Expensify/Zoho/Wave/Dext/Fetch = cloud OCR + humans; indie apps market on-device), Apple's free on-device stack verified against the iOS SDK (RecognizeDocumentsRequest + DataDetection.moneyAmount, VisionKit document camera / .currency live scan, Foundation Models), free/OSS/cloud options evaluated against "money data never leaves the phone", and the decisions (D1–D8).
• Pure ReceiptParser (Utilities/Receipt/): rows clustered from OCR line boxes, receipt amount grammar (thousands separators, comma decimals, whole pesos, OCR digit confusions, %/dates/ids ignored), es/en label hierarchy with exclusions (SUBTOTAL, IVA, PROPINA, EFECTIVO, CAMBIO, TARJETA, PUNTOS…), scored candidates + ranked alternatives, merchant (brand map + prettifying), printed date (dd/mm vs mm/dd by language signal, plausibility window), category hint onto the five chips.
• OCR fixes (Utilities/ReceiptOCR.swift): image orientation is now passed to Vision (was dropped → portrait receipts read sideways), recognition languages es+en resolved at runtime (was en-US default), single RecognizeDocumentsRequest with Apple's money/date detectors as a second opinion, RecognizeTextRequest fallback, decode/downscale off the main actor.
• Camera (CameraManager rewrite): RotationCoordinator for correct EXIF on stills, guarded async capturePhoto() (the old shutter could crash on an unconfigured session), torch, gallery import (PhotosPicker), the never-drawn per-frame rectangle detection removed, retain cycle gone. VNDocumentCameraViewController wrapped behind FeatureFlags.useSystemDocumentCamera (default off) so both capture surfaces can be A/B'd on a real device.
• Review screen replaces the disabled-text-field card: thumbnail, editable amount (keypad), "also on the receipt" chips, merchant, date (from the receipt / today), category chips pre-selected, honest copy for low confidence / nothing found, failed state that never dead-ends, VoiceOver announcements + modal overlays, Warm Meadow tokens, all strings via Strings.swift with es-419. Both entry points (+ sheet and Money tab) migrated. Saved rows now carry merchant + receipt date + category (was "Recibo escaneado", now, nil).
• Deleted CameraViewModel, TextRecognizer, OCRUtilities (dead), TotalConfirmationView. CLAUDE.md invariant 7 corrected + new invariant 10; gotchas.yaml entry.

Why

The old scanner systematically recorded the cash tendered instead of the total on Mexican receipts (TOTAL / EFECTIVO / CAMBIO → 100.00 instead of 41.18), dropped leading digits (1234.56 → 234.56), rejected coffees (< 10), read portrait photos without orientation, and none of it was testable. Spike details in docs/spikes/receipt-scan-spike.md §1.2.

Test plan

• xcodebuild build -scheme Savely (iPhone 17 Pro sim, Xcode 27 beta locally)
• xcodebuild test -scheme Savely — 102/102 unit tests, incl. new ReceiptParserTests, ReceiptFixtureTests (16 hand-authored JSON fixtures), ReceiptOCRIntegrationTests (real Vision on a script-rendered receipt: total 57.50, merchant, date, subtotal alternative; and the same bitmap rotated + tagged sideways still reads)
• swiftlint --strict clean on all touched files
• Simulator UI test ReceiptScanUITests (needs xcrun simctl addmedia <udid> SavelyTests/Fixtures/Images/synthetic-oxxo.png): + → Scan a receipt → Choose from Photos → review shows 57.50 / OXXO / 14-08 / Food → Save → row appears in Money
• Manual on device (cannot be done in the Simulator — no camera): shutter capture in portrait and landscape, torch, "Open Settings" round trip after denying access, and flip FeatureFlags.useSystemDocumentCamera = true to compare the system document camera
• Manual: collect real es-MX/US receipts with the DEBUG "Export OCR dump" button, anonymize, drop into SavelyTests/Fixtures/Receipts/ (this is where accuracy numbers will come from — the current fixtures prove rules, not real-world accuracy)

Risks

• Fixtures are hand-authored layouts (each says so in source); real-receipt accuracy is unmeasured until phase 2. Everything the parser produces is a draft the user confirms — nothing is saved silently.
• ExpenseTrackerViewModel.addExpense(description:amount:date:category:) no longer flips showError (the scanner shows the message inline); the form path still does. Two hardcoded error literals there moved to Strings.Errors.
• pbxproj edited by script (files added/removed, SavelyTests/Fixtures folder reference in the test target's Resources phase). Please open once in Xcode.
• Locally built with Xcode 27 beta / iOS 27 SDK; CI pins Xcode 26.0 — the APIs used are iOS 26 (RecognizeDocumentsRequest, DataDetection), so CI should compile; watch the first run.

Checklist

• Branch named with approved prefix (feature/)
• Commits follow Conventional Commits
• No hardcoded user-facing strings (all routed through Strings.swift)
• No secrets staged
• CLAUDE.md / knowledge files updated
• Tests added or updated for behavior changes