feat: email receipts and repair estimates

Backend:
- Server-side HTML email templates (receipt + estimate) with inline CSS
- POST /v1/transactions/:id/email-receipt with per-transaction rate limiting
- POST /v1/repair-tickets/:id/email-estimate with per-ticket rate limiting
- customerEmail field added to receipt and ticket detail responses
- Test email provider for API tests (logs instead of sending)

Frontend:
- POS payment dialog Email button enabled with inline email input
- Pre-fills customer email from linked account
- Repair ticket detail page has Email Estimate button with dialog
- Pre-fills from account email

Tests:
- 12 unit tests for email template renderers
- 8 API tests for email receipt/estimate endpoints and validation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/backend/api-tests/suites/pos.ts

@@ -1051,4 +1051,48 @@ suite('POS', { tags: ['pos'] }, (t) => {
     // Cleanup
     await t.api.post(`/v1/drawer/${drawer.data.id}/close`, { closingBalance: 100 })
   })
+
+  // ─── Email Receipt ──────────────────────────────────────────────────────────
+
+  t.test('emails a receipt for a completed transaction', { tags: ['transactions', 'email'] }, async () => {
+    // Create and complete a transaction
+    const txn = await t.api.post('/v1/transactions', { transactionType: 'sale', locationId: LOCATION_ID })
+    await t.api.post(`/v1/transactions/${txn.data.id}/line-items`, { description: 'Email Test Item', qty: 1, unitPrice: 25 })
+    await t.api.post(`/v1/transactions/${txn.data.id}/complete`, { paymentMethod: 'card_present' })
+
+    const res = await t.api.post(`/v1/transactions/${txn.data.id}/email-receipt`, { email: 'customer@test.com' })
+    t.assert.status(res, 200)
+    t.assert.equal(res.data.message, 'Receipt sent')
+    t.assert.equal(res.data.sentTo, 'customer@test.com')
+  })
+
+  t.test('rejects email receipt with invalid email', { tags: ['transactions', 'email', 'validation'] }, async () => {
+    const txn = await t.api.post('/v1/transactions', { transactionType: 'sale', locationId: LOCATION_ID })
+    await t.api.post(`/v1/transactions/${txn.data.id}/line-items`, { description: 'Bad Email Item', qty: 1, unitPrice: 10 })
+    await t.api.post(`/v1/transactions/${txn.data.id}/complete`, { paymentMethod: 'card_present' })
+
+    const res = await t.api.post(`/v1/transactions/${txn.data.id}/email-receipt`, { email: 'not-an-email' })
+    t.assert.status(res, 400)
+  })
+
+  t.test('rejects email receipt with missing body', { tags: ['transactions', 'email', 'validation'] }, async () => {
+    const txn = await t.api.post('/v1/transactions', { transactionType: 'sale', locationId: LOCATION_ID })
+    await t.api.post(`/v1/transactions/${txn.data.id}/line-items`, { description: 'No Body Item', qty: 1, unitPrice: 10 })
+    await t.api.post(`/v1/transactions/${txn.data.id}/complete`, { paymentMethod: 'card_present' })
+
+    const res = await t.api.post(`/v1/transactions/${txn.data.id}/email-receipt`, {})
+    t.assert.status(res, 400)
+  })
+
+  t.test('receipt response includes customerEmail', { tags: ['transactions', 'email'] }, async () => {
+    // Create account with email
+    const acct = await t.api.post('/v1/accounts', { name: 'Email Customer', email: 'acct@test.com', billingMode: 'consolidated' })
+    const txn = await t.api.post('/v1/transactions', { transactionType: 'sale', locationId: LOCATION_ID, accountId: acct.data.id })
+    await t.api.post(`/v1/transactions/${txn.data.id}/line-items`, { description: 'Account Item', qty: 1, unitPrice: 50 })
+    await t.api.post(`/v1/transactions/${txn.data.id}/complete`, { paymentMethod: 'card_present' })
+
+    const receipt = await t.api.get(`/v1/transactions/${txn.data.id}/receipt`)
+    t.assert.status(receipt, 200)
+    t.assert.equal(receipt.data.customerEmail, 'acct@test.com')
+  })
 })