Fix Dashboard /_blazor endpoint conflict with host Blazor apps

[lahma]

Summary

Fixes #2974

• Add MapQuartzDashboard(existingComponents) overload that integrates into the host's existing Blazor setup via AddAdditionalAssemblies, avoiding a duplicate /_blazor SignalR endpoint
• Extract inline JS from QuartzDashboardApp.razor into a Blazor JS initializer (Quartz.Dashboard.lib.module.js) that auto-loads in both standalone and integrated modes
• Inject dashboard CSS via <HeadContent> in DashboardLayout so it works when rendered inside a host app's root component
• Add @layout DashboardLayout scoped to Pages/ so dashboard pages render correctly when discovered by the host's Router
• Remove HealthChecks UI packages and configuration from example app

Usage for apps with existing Blazor Server setup

var blazor = endpoints.MapRazorComponents<App>()
    .AddInteractiveServerRenderMode();

endpoints.MapQuartzDashboard(blazor);

Standalone usage (unchanged)

endpoints.MapQuartzDashboard();

Test plan

• Build passes with zero warnings/errors
• Quartz.Examples.AspNetCore — dashboard at /quartz renders and navigates correctly (standalone mode)
• Host app with its own MapRazorComponents<App>().AddInteractiveServerRenderMode() — dashboard works via MapQuartzDashboard(blazor) without /_blazor conflict

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
10 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud