Apply .NET Aspire orchestration to Chapter 2

[Copilot]

📋 Description

Replaces Docker Compose with .NET Aspire for Chapter 2, matching the orchestration approach used in Chapter 1 (PR #223).

Key changes:

• Aspire AppHost project: Configures PostgreSQL (14.3) with pgAdmin, wires database references using Chapter 2's hierarchical config format (Module__ConnectionStrings)
• Central Package Management: Adds Aspire packages (Aspire.Hosting.AppHost 9.0.0, Aspire.Hosting.PostgreSQL 9.0.0, KubernetesClient 17.0.14) to Directory.Packages.props
• Docker artifacts removed: docker-compose.yml, Dockerfile, .dockerignore
• Documentation updated: README now documents Aspire launch with observability dashboard

Configuration difference from Chapter 1:

// Chapter 2 uses hierarchical module config format
builder.AddProject<Fitnet>("fitnet")
    .WithReference(fitnetDatabase, "Passes__ConnectionStrings")
    .WithReference(fitnetDatabase, "Contracts__ConnectionStrings")
    // vs Chapter 1's flat format: "Passes", "Contracts"

Integration tests verified (Passes: 4/4, Contracts: 7/7).

📦 PR Includes

• Feature added 🆕
• Bug fix 🐛
• Code refactor 🔄
• Documentation update 📚
• Tests added/updated 🧪
• Other: (describe)

🚫 PR Does Not Include

• Breaking changes ❌
• Major architectural changes 🏗️
• Unrelated features/tasks 🚫

💡 Additional Notes

Chapter 2's Central Package Management required adding Aspire packages to Directory.Packages.props rather than inline project references. The Module__ConnectionStrings format matches Chapter 2's existing configuration hierarchy in appsettings.json.

Original prompt

chapter 2 apply aspire like in chapter 1

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