Add WisePOS E in-person card payments (Stripe Terminal)

Server-driven Stripe Terminal integration for taking in-person card payments
against an invoice, running on the same Stripe Connect connected account used
for online payments. No native app or Terminal SDK — the WisePOS E is driven
from the web backend via Stripe's REST API.

- Domain: TerminalReader entity + status enum, PaymentMethod.CardReader,
  Company.StripeTerminalLocationId / TerminalSurchargeEnabled, DbSet + tenant
  filter + indexes, IUnitOfWork repo, migration AddTerminalReaders (additive).
- StripeConnectService: location/reader registration, list, delete, process
  payment on reader, status poll, cancel, and a test-mode simulated tap. All
  routed to the connected account like the existing online-payment methods.
- TerminalController: admin reader management + per-invoice ProcessPayment,
  PaymentStatus (poll), CancelPayment, SimulateTap (test mode only). Stores the
  PaymentIntent id on the invoice; the webhook remains the authoritative writer.
- PaymentController webhook: HandlePaymentSucceededAsync records source=terminal
  payments as CardReader (online path unchanged — no source key means no change);
  new terminal.reader.action_failed handler for declines/timeouts (notification
  only, no ledger mutation). Refund path reused unchanged.
- UI: Card Readers settings tab (register/list/deactivate + in-person surcharge
  toggle, default off with a compliance warning) and an invoice "Take Card
  Payment" modal with live status polling. External JS per project convention.
- Feature bundled with the existing online-payments entitlement (no new plan
  flag); additionally requires StripeConnectStatus == Active.
- Help: HelpKnowledgeBase + Invoices help article updated.
- Tests: TerminalController validation + surcharge-routing tests (241 pass).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Application/DTOs/Terminal/TerminalDtos.cs

@@ -0,0 +1,29 @@
+namespace PowderCoating.Application.DTOs.Terminal
+{
+    /// <summary>
+    /// Minimal postal address used to create a Stripe Terminal Location. Kept in the Application
+    /// layer so <c>IStripeConnectService</c> doesn't leak Stripe SDK types to controllers.
+    /// </summary>
+    public class TerminalAddressDto
+    {
+        public string Line1 { get; set; } = string.Empty;
+        public string City { get; set; } = string.Empty;
+        public string State { get; set; } = string.Empty;
+        public string PostalCode { get; set; } = string.Empty;
+        public string Country { get; set; } = "US";
+    }
+
+    /// <summary>
+    /// A Stripe Terminal reader as returned by the Stripe API, projected to a plain DTO for the
+    /// settings page and reconciliation. Stripe remains the source of truth for live network status.
+    /// </summary>
+    public class TerminalReaderDto
+    {
+        public string StripeReaderId { get; set; } = string.Empty;
+        public string Label { get; set; } = string.Empty;
+        public string DeviceType { get; set; } = string.Empty;
+        public string? SerialNumber { get; set; }
+        public string? NetworkStatus { get; set; }   // "online" / "offline"
+        public DateTime? LastSeenAt { get; set; }
+    }
+}