feat(ocr): Tesseract.js as default scanner, AI as opt-in per port

The mobile receipt scanner now runs Tesseract.js in-browser by default —
on-device, free, and image bytes never leave the device. AI providers
(OpenAI / Claude) become a per-port opt-in for higher accuracy on
hard-to-read receipts.

- Lazy-load Tesseract WASM in src/lib/ocr/tesseract-client.ts (5 MB
  bundle dynamic-imports on first scan, not in main chunk)
- Heuristic parser src/lib/ocr/parse-receipt-text.ts extracts vendor,
  date, amount, currency, and line items from raw OCR text
- New port-scoped aiEnabled flag on OcrConfig (defaults false). Resolved
  flag never inherits from the global row — each port admin opts in
  independently
- Scan endpoint short-circuits to manual-mode when aiEnabled=false so
  the AI provider is never invoked unless the admin has flipped the
  switch
- Scan UI runs Tesseract first, then asks the server whether AI is
  enabled — uses the AI result only when its confidence beats Tesseract;
  network failures degrade gracefully to the local parse
- Admin OCR-settings form gains the per-port aiEnabled checkbox

Tests: 756/756 vitest (was 747) — +7 parser unit tests, +2 aiEnabled
config tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/ocr/parse-receipt-text.test.ts

@@ -0,0 +1,101 @@
+import { describe, it, expect } from 'vitest';
+
+import { parseReceiptText } from '@/lib/ocr/parse-receipt-text';
+
+describe('parseReceiptText', () => {
+  it('extracts vendor, date, total, currency, and line items from a basic English receipt', () => {
+    const text = `
+Marina Fuel Station
+123 Harbor Way
+Anguilla
+
+Date: 2026-04-28
+
+Diesel       45.00
+Pump Fee     5.00
+Subtotal    50.00
+Tax          5.00
+TOTAL       55.00
+
+Thank you!
+`;
+    const r = parseReceiptText({ text, ocrConfidence: 92 });
+    expect(r.establishment).toBe('Marina Fuel Station');
+    expect(r.date).toBe('2026-04-28');
+    expect(r.amount).toBe(55);
+    expect(r.lineItems.length).toBeGreaterThanOrEqual(1);
+    expect(r.lineItems[0]!.description).toMatch(/diesel/i);
+    expect(r.confidence).toBeGreaterThan(0.5);
+  });
+
+  it('parses European date and comma-decimal amount', () => {
+    const text = `
+Boulangerie du Port
+Rue de la Marina
+
+28/04/2026
+
+Pain      3,50
+Café      2,50
+
+Total: 6,00 €
+`;
+    const r = parseReceiptText({ text });
+    expect(r.date).toBe('2026-04-28');
+    expect(r.amount).toBe(6);
+    expect(r.currency).toBe('EUR');
+  });
+
+  it('handles ISO currency codes when no symbol is present', () => {
+    const text = `
+Receipt
+Acme Co.
+Total 199.00 USD
+`;
+    const r = parseReceiptText({ text });
+    expect(r.currency).toBe('USD');
+  });
+
+  it('returns null fields and zero confidence when nothing parseable', () => {
+    const r = parseReceiptText({ text: '@@@\n!!!\n###' });
+    expect(r.establishment).toBeNull();
+    expect(r.amount).toBeNull();
+    expect(r.date).toBeNull();
+    expect(r.confidence).toBe(0);
+  });
+
+  it('prefers grand total over subtotal even when subtotal is named "total"', () => {
+    const text = `
+Vendor X
+
+Item A   10.00
+Item B   20.00
+Subtotal 30.00
+Tax       3.00
+Grand Total 33.00
+`;
+    const r = parseReceiptText({ text });
+    expect(r.amount).toBe(33);
+  });
+
+  it('skips obvious total/subtotal lines when extracting line items', () => {
+    const text = `
+Boutique
+Shirt    25.00
+Tie      15.00
+Subtotal 40.00
+Tax       4.00
+Total    44.00
+`;
+    const r = parseReceiptText({ text });
+    const descriptions = r.lineItems.map((li) => li.description.toLowerCase());
+    expect(descriptions.some((d) => d.includes('subtotal'))).toBe(false);
+    expect(descriptions.some((d) => d.includes('total'))).toBe(false);
+    expect(descriptions.some((d) => d.includes('tax'))).toBe(false);
+  });
+
+  it('rejects implausible dates', () => {
+    const r = parseReceiptText({ text: 'Random 1899-04-12 noise' });
+    expect(r.date).toBeNull();
+  });
+});