Add comprehensive XML documentation to PocketBaseSharp project

[Copilot]

This PR addresses the lack of proper method documentation throughout the PocketBaseSharp project by adding comprehensive XML documentation comments to all public APIs.

What was added

Core Classes

• PocketBase: Complete class documentation including constructor parameters, all HTTP methods (Send, SendAsync, BuildUrl), event delegates, and service properties
• BaseService & BaseCrudService: Full documentation for the inheritance hierarchy to guide developers creating custom services

Service Classes

All service classes now have comprehensive documentation:

• AdminService: Admin authentication and management operations
• BackupService: Database backup retrieval and management
• SettingsService: Application settings with methods like GetAll, Update, TestS3, TestEmail
• CollectionService: Collection schema management including import/export functionality
• RecordService: Record CRUD operations and file management
• RealTimeService: WebSocket connections and real-time subscriptions via Server-Sent Events
• CollectionAuthService: Generic authentication services for custom collections
• UserService: User account management (enhanced existing documentation)
• LogService: Request logging and statistics (enhanced existing documentation)

Benefits

For Developers

• IntelliSense support: All public methods now show helpful parameter descriptions and return value information
• Better discoverability: Clear descriptions of what each service does and when to use it
• Parameter guidance: Detailed explanations of all method parameters including optional ones
• Type safety: Generic type constraints are properly documented

For Documentation

• API reference generation: XML comments enable automatic API documentation generation
• Consistent style: All documentation follows C# XML documentation standards
• Usage examples: Method descriptions include context about when and how to use them

Example of improvements

Before:

public class PocketBase
{
    public Task<Result<T>> SendAsync<T>(string path, HttpMethod method, ...)
}

After:

/// <summary>
/// Main client class for interacting with PocketBase backend services.
/// Provides access to all PocketBase APIs including authentication, collections, real-time subscriptions, and more.
/// </summary>
public class PocketBase
{
    /// <summary>
    /// Sends an asynchronous HTTP request to the PocketBase API and deserializes the response to the specified type.
    /// </summary>
    /// <typeparam name="T">The type to deserialize the response to</typeparam>
    /// <param name="path">The API endpoint path (without base URL)</param>
    /// <param name="method">The HTTP method to use for the request</param>
    /// <param name="headers">Optional HTTP headers to include with the request</param>
    /// <param name="query">Optional query parameters to append to the URL</param>
    /// <param name="body">Optional request body data</param>
    /// <param name="files">Optional files to upload with the request</param>
    /// <param name="cancellationToken">Cancellation token to cancel the operation</param>
    /// <returns>A Result containing the deserialized response of type T or an error</returns>
    public Task<Result<T>> SendAsync<T>(string path, HttpMethod method, ...)
}

Validation

• ✅ Project builds successfully with all documentation
• ✅ No functional changes or breaking changes to existing APIs
• ✅ All public methods, constructors, and properties documented
• ✅ Follows C# XML documentation standards consistently

This significantly improves the developer experience when working with PocketBaseSharp by providing clear, comprehensive documentation for all public APIs.

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