Add Customer Intake Kiosk help article and knowledge base entry

- New Help article at /Help/CustomerIntakeKiosk covering setup, in-person
  and remote intake flows, what happens on submission, reviewing intakes,
  and troubleshooting (signature pad, connection issues, seed data)
- Add kiosk entry to _HelpNav under Operations
- Update HelpKnowledgeBase: nav overview, full kiosk section, two new
  common workflow entries (walk-in kiosk and remote intake)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Controllers/HelpController.cs

@@ -125,5 +125,13 @@ namespace PowderCoating.Web.Controllers
         {
             return View();
         }
+
+        /// <summary>
+        /// Serves the Customer Intake Kiosk help article explaining the tablet kiosk setup, the staff-triggered intake flow, and the Intakes review page.
+        /// </summary>
+        public IActionResult CustomerIntakeKiosk()
+        {
+            return View();
+        }
     }
 }