Implement NetEvolve.HealthChecks.Azure.Files package for Azure File Storage health checks

[Copilot]

This PR implements a comprehensive health check package for Azure File Storage, following the established patterns used by other Azure service packages in this repository.

What's Added

Core Health Checks

• FileShareAvailableHealthCheck: Validates that a specific Azure File Share is reachable and accessible
• FileServiceAvailableHealthCheck: Validates that the Azure File Service itself is reachable and responsive

Authentication Support

The package supports all standard Azure authentication modes:

• ServiceProvider: Uses pre-registered ShareServiceClient from dependency injection
• ConnectionString: Direct connection string authentication
• SharedKey: Account name and key authentication
• DefaultAzureCredentials: Managed identity and default credential chain
• AzureSasCredential: SAS token authentication

Configuration Options

Both health checks support flexible configuration:

• Configuration-based setup via appsettings.json
• Options-based setup with inline configuration
• Configurable timeouts with proper degraded status handling
• Comprehensive validation with detailed error messages

Example Usage

// Configuration-based approach
services.AddHealthChecks()
    .AddFileShareAvailability("my-fileshare");

// Options-based approach  
services.AddHealthChecks()
    .AddFileShareAvailability("my-fileshare", options =>
    {
        options.ShareName = "documents";
        options.ConnectionString = "DefaultEndpointsProtocol=https;...";
        options.Timeout = 5000;
    });

Package Integration

• Added Azure.Storage.Files.Shares package dependency to central package management
• Updated main NetEvolve.HealthChecks.Azure bundle package to include Files
• Added Files to the supported services documentation

Comprehensive Testing

• Unit Tests: Complete validation coverage for all configuration scenarios, authentication modes, and error conditions
• Integration Tests: Real-world testing using the existing AzuriteAccess test infrastructure
• 100+ test cases covering edge cases and validation scenarios

The implementation follows identical patterns to existing Azure packages (Blobs, Tables, Queues, ServiceBus) ensuring consistency and maintainability.

Fixes #37.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• aka.ms
  • Triggering command: curl -I -sSL --retry 5 --retry-delay 2 --connect-timeout 15 REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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