feat(print): dashboard UI for print servers + auto-discovered printer pickers

Phase 4 (final). Settings → Printers now has a "Print servers" section: add a
print server (issues a one-time pairing code with steps), see each agent's online
status, its auto-discovered printers, test any of them, and revoke. Receipt,
kitchen and per-station printers can now be picked from a dropdown of discovered
devices instead of typing an IP (manual IP stays as fallback). Wires the device
mappings through the branch print-settings + kitchen-station DTOs/services and adds
the device-test endpoint. fa/en/ar strings added.

Completes the cloud↔LAN print-agent feature (entities/hub → routing → agent → UI).
Remaining polish: agent system-tray + run-at-login + installer, optional LAN scan.

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

src/Meezi.API/Models/Printing/PrintDtos.cs

@@ -12,7 +12,9 @@ public record BranchPrintSettingsDto(
     string? ReceiptFooter,
     string? WifiPassword,
     string? PosDeviceIp,
-    int? PosDevicePort);
+    int? PosDevicePort,
+    string? ReceiptPrintDeviceId,
+    string? KitchenPrintDeviceId);
 
 public record PatchBranchPrintSettingsRequest(
     string? ReceiptPrinterIp,
@@ -25,7 +27,9 @@ public record PatchBranchPrintSettingsRequest(
     string? ReceiptFooter,
     string? WifiPassword,
     string? PosDeviceIp,
-    int? PosDevicePort);
+    int? PosDevicePort,
+    string? ReceiptPrintDeviceId,
+    string? KitchenPrintDeviceId);
 
 public record PosPaymentRequest(string OrderId, decimal Amount);