Introduce .UseInvariantCulture() extension methods for host and web builders

[Copilot]

Added

• Extension method IHostBuilder.UseInvariantCulture() in Arc.Core configures default thread cultures to InvariantCulture
• Extension method WebApplicationBuilder.UseInvariantCulture() in Arc configures thread cultures and request localization to InvariantCulture only
• Extension method WebApplication.UseInvariantCulture() in Arc applies invariant culture middleware to the request pipeline

Usage:

// ASP.NET Core
var builder = WebApplication.CreateBuilder(args);
builder.UseInvariantCulture();
builder.AddCratisArc();

var app = builder.Build();
app.UseInvariantCulture();
app.UseCratisArc();

// Generic Host
var builder = Host.CreateDefaultBuilder(args);
builder.UseInvariantCulture();
builder.AddCratisArcCore();

Implementation approach:

• Sets CultureInfo.DefaultThreadCurrentCulture and CultureInfo.DefaultThreadCurrentUICulture to InvariantCulture ensuring all threads use invariant culture
• Configures RequestLocalizationOptions with only InvariantCulture and clears all culture providers to prevent runtime culture changes
• Aligns with existing codebase patterns that already use InvariantCulture for JSON and MongoDB serialization

Original prompt

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This section details on the original issue you should resolve

<issue_title>Introduce a .UseInvariantCulture() extension method for host builder and Web builders</issue_title>
<issue_description>It should configure all places that needs to be configured for culture.
Research the best way to guarantee invariant culture at runtime.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Introduce a .UseInvariantCulture() extension method for host builder and Web builders #61

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