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>

web/dashboard/messages/en.json

@@ -370,6 +370,24 @@
       "empty": "No stations yet. Add Kitchen and Bar to print their items separately.",
       "deleteConfirm": "Delete station “{name}”? Its categories will fall back to the kitchen printer.",
       "saveError": "Failed to save the station."
+    },
+    "agents": {
+      "title": "Print servers (auto-discovery)",
+      "hint": "Install the Meezi print agent on the cash PC to auto-detect its USB & network printers and print through it.",
+      "add": "Add print server",
+      "pairingTitle": "Enter this code in the print agent on the cash PC:",
+      "pairingSteps": "Install and run the Meezi Print Agent on the PC connected to the printers, then enter this code. It is valid for 15 minutes.",
+      "empty": "No print server connected yet.",
+      "online": "Online",
+      "offline": "Offline",
+      "noDevices": "Discovering printers…",
+      "test": "Test",
+      "receiptVia": "Receipt printer (via server)",
+      "kitchenVia": "Kitchen printer (via server)",
+      "viaServer": "Printer (via server)",
+      "useIpInstead": "— Use manual IP —",
+      "revokeConfirm": "Remove print server “{name}”? It will no longer be able to print.",
+      "codeError": "Could not create code."
     }
   },
   "receipt": {