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/admin/src/components/pos/pos-payment-dialog.tsx

@@ -84,6 +84,7 @@ export function POSPaymentDialog({ open, onOpenChange, paymentMethod, transactio
     queryKey: ['pos', 'receipt', result?.id],
     queryFn: () => api.get<{
       transaction: Transaction & { lineItems: { description: string; qty: number; unitPrice: string; taxAmount: string; lineTotal: string; discountAmount: string }[] }
+      customerEmail: string | null
       company: { name: string; phone: string | null; email: string | null; address: { street?: string; city?: string; state?: string; zip?: string } | null }
       location: { name: string; phone: string | null; email: string | null; address: { street?: string; city?: string; state?: string; zip?: string } | null }
     }>(`/v1/transactions/${result!.id}/receipt`),
@@ -91,6 +92,19 @@ export function POSPaymentDialog({ open, onOpenChange, paymentMethod, transactio
   })
 
   const [showReceipt, setShowReceipt] = useState(false)
+  const [emailMode, setEmailMode] = useState(false)
+  const [emailAddress, setEmailAddress] = useState('')
+  const [emailSent, setEmailSent] = useState(false)
+
+  const emailReceiptMutation = useMutation({
+    mutationFn: () => api.post<{ message: string }>(`/v1/transactions/${result!.id}/email-receipt`, { email: emailAddress }),
+    onSuccess: () => {
+      toast.success('Receipt emailed')
+      setEmailMode(false)
+      setEmailSent(true)
+    },
+    onError: (err) => toast.error(err.message),
+  })
 
   if (completed && result) {
     const changeGiven = parseFloat(result.changeGiven ?? '0')
@@ -140,14 +154,47 @@ export function POSPaymentDialog({ open, onOpenChange, paymentMethod, transactio
               )}
             </div>
 
-            <div className="w-full grid grid-cols-2 gap-2">
-              <Button variant="outline" className="h-11 gap-2" onClick={() => setShowReceipt(true)}>
-                <Printer className="h-4 w-4" />Receipt
-              </Button>
-              <Button variant="outline" className="h-11 gap-2" disabled>
-                <Mail className="h-4 w-4" />Email
-              </Button>
-            </div>
+            {emailMode ? (
+              <div className="w-full space-y-2">
+                <Label className="text-xs text-muted-foreground">Email receipt to:</Label>
+                <div className="flex gap-2">
+                  <Input
+                    type="email"
+                    value={emailAddress}
+                    onChange={(e) => setEmailAddress(e.target.value)}
+                    placeholder="customer@example.com"
+                    className="h-9"
+                    autoFocus
+                  />
+                  <Button
+                    size="sm"
+                    className="h-9 px-4"
+                    onClick={() => emailReceiptMutation.mutate()}
+                    disabled={!emailAddress || emailReceiptMutation.isPending}
+                  >
+                    {emailReceiptMutation.isPending ? 'Sending...' : 'Send'}
+                  </Button>
+                </div>
+                <Button variant="ghost" size="sm" className="text-xs" onClick={() => setEmailMode(false)}>Cancel</Button>
+              </div>
+            ) : (
+              <div className="w-full grid grid-cols-2 gap-2">
+                <Button variant="outline" className="h-11 gap-2" onClick={() => setShowReceipt(true)}>
+                  <Printer className="h-4 w-4" />Receipt
+                </Button>
+                <Button
+                  variant="outline"
+                  className="h-11 gap-2"
+                  onClick={() => {
+                    setEmailAddress(receiptData?.customerEmail ?? '')
+                    setEmailMode(true)
+                  }}
+                  disabled={emailSent}
+                >
+                  <Mail className="h-4 w-4" />{emailSent ? 'Sent' : 'Email'}
+                </Button>
+              </div>
+            )}
 
             <Button className="w-full h-12 text-base" onClick={handleDone}>
               New Sale