Demo reset + dev banner suppression for DEMO company

- DemoController: company-code-gated reset action (DEMO only, CSRF protected)
- SeedDataService.Remove: FK-safe topological pre-sweep, all deletes scoped to companyId
- SeedDataService: clock entries, extra seed data, updated customer/worker/job-status seeders
- CompanySettingsController + Index.cshtml: Reset Demo Data button for DEMO company users
- ReportsController + FinancialReportService: supporting report fixes
- _Layout.cshtml: suppress env banner when current company is DEMO (all auth paths)

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

src/PowderCoating.Web/Controllers/CompanySettingsController.cs

@@ -181,6 +181,8 @@ public class CompanySettingsController : Controller
                 ? (DateTime?)company.BookLockedThrough.Value.ToLocalTime()
                 : null;
 
+            ViewBag.IsDemoCompany = company.CompanyCode == "DEMO";
+
             return View(dto);
         }
         catch (FormatException fex)