Add Luna.Configuration with TOML-based agent and provider config

Implement configuration system with embedded TOML resources for agent
and provider definitions, custom IConfigurationSource/Provider for
agent and provider options, and DI extension methods. Includes config
models for agents, providers, sessions, and Telegram integration.

Luna.Configuration/Services/Providers/ProviderOptionsConfigurationProvider.cs

@@ -0,0 +1,32 @@
+using System.Reflection;
+using Microsoft.Extensions.Configuration;
+
+namespace Luna.Configuration.Services.Providers;
+
+internal class ProviderOptionsConfigurationProvider(IEnumerable<(string Name, ProviderOptions Options)> providerOptions)
+    : ConfigurationProvider
+{
+    public override void Load()
+    {
+        foreach (var (name, options) in providerOptions)
+        {
+            var keyPrefix = $"Providers:{name}";
+
+            foreach (var property in options.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public))
+            {
+                var value = property.GetValue(options);
+
+                if (value is string[] array)
+                {
+                    for (var i = 0; i < array.Length; i++)
+                        Data[$"{keyPrefix}:{property.Name}:{i}"] = array[i];
+                }
+                else
+                {
+                    Data[$"{keyPrefix}:{property.Name}"] = value?.ToString();
+                }
+            }
+        }
+    }
+}
+

Luna.Configuration/Services/Providers/ProviderOptionsConfigurationSource.cs

@@ -0,0 +1,13 @@
+using Microsoft.Extensions.Configuration;
+
+namespace Luna.Configuration.Services.Providers;
+
+internal class ProviderOptionsConfigurationSource(string? searchPath = null)
+    : IConfigurationSource
+{
+    private readonly ProviderOptionsProvider optionsProvider = new(searchPath);
+
+    public IConfigurationProvider Build(IConfigurationBuilder builder)
+        => new ProviderOptionsConfigurationProvider(optionsProvider.GetProviderOptions());
+}
+

Luna.Configuration/Services/Providers/ProviderOptionsProvider.cs

@@ -0,0 +1,63 @@
+using System.Text.RegularExpressions;
+using Tomlyn;
+
+namespace Luna.Configuration.Services.Providers;
+
+internal sealed class ProviderOptionsProvider(string? searchPath = null)
+{
+    private readonly EmbeddedResourceLoader embeddedResourceLoader = new();
+
+    public IEnumerable<(string Name, ProviderOptions Options)> GetProviderOptions()
+    {
+        return string.IsNullOrWhiteSpace(searchPath)
+            ? GetProviderOptionsFromEmbeddedResources()
+            : GetProviderOptionsFromFiles();
+    }
+
+    private IEnumerable<(string Name, ProviderOptions Options)> GetProviderOptionsFromFiles()
+    {
+        ArgumentException.ThrowIfNullOrEmpty(searchPath);
+
+        var files = Directory.Exists(searchPath)
+            ? Directory.EnumerateFiles(searchPath, "Provider.*.toml")
+            : [];
+        
+        foreach (var file in files)
+        {
+            var name = Path.GetFileName(file).ToProviderName();
+            using var reader = File.OpenText(file);
+            var providerOptions = TomlSerializer.Deserialize<ProviderOptions>(reader);
+
+            yield return (name, providerOptions
+                ?? throw new FormatException($"Invalid provider config file: {file}"));
+        }
+    }
+
+    private IEnumerable<(string Name, ProviderOptions Options)> GetProviderOptionsFromEmbeddedResources()
+    {
+        var resources = embeddedResourceLoader.ListResources("Provider.*.toml");
+        foreach (var resource in resources)
+        {
+            var name = resource.ToProviderName();
+            var content = embeddedResourceLoader.LoadAsync(resource).GetAwaiter().GetResult();
+            var providerOptions = TomlSerializer.Deserialize<ProviderOptions>(content);
+
+            yield return (name, providerOptions
+                ?? throw new FormatException($"Invalid provider config embedded resource: {resource}"));
+        }
+    }
+}
+
+internal static partial class ProviderStringExtensions
+{
+    [GeneratedRegex(@"Provider\.(.+)\.toml", RegexOptions.IgnoreCase | RegexOptions.Compiled)]
+    private static partial Regex ProviderNameRegex { get; }
+
+    extension(string str)
+    {
+        public string ToProviderName() => ProviderNameRegex.Match(str) is { Success: true } match
+            ? match.Groups[1].Value
+            : throw new FormatException($"Invalid provider config file name: {str}");
+    }
+}
+