fix: Implement required interface methods and address nullable warnings

- Added GetConfiguration() and SaveConfigurationAsync() methods to ConfigService
- Added synchronous file reading for GetConfiguration()
- Fixed nullable reference type warnings in LoggingService
- Added nullable annotations to interface definitions
- Enabled nullable reference types for affected files

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

src/Core/Interfaces.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Threading;

src/Services/ConfigService.cs

@@ -35,6 +35,44 @@ namespace TransmissionRssManager.Services
             _logger.LogInformation($"Using configuration file: {_configFilePath}");
         }
 
+        // Implement the interface methods required by IConfigService
+        public AppConfig GetConfiguration()
+        {
+            // Non-async method required by interface
+            if (_cachedConfig != null)
+            {
+                return _cachedConfig;
+            }
+
+            try
+            {
+                // Load synchronously since this is a sync method
+                _cachedConfig = LoadConfigFromFileSync();
+                return _cachedConfig;
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Error loading configuration, using default values");
+                return CreateDefaultConfig();
+            }
+        }
+
+        public async Task SaveConfigurationAsync(AppConfig config)
+        {
+            try
+            {
+                _cachedConfig = config;
+                await SaveConfigToFileAsync(config);
+                _logger.LogInformation("Configuration saved successfully to file");
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Error saving configuration to file");
+                throw;
+            }
+        }
+
+        // Additional methods for backward compatibility
         public async Task<AppConfig> GetConfigAsync()
         {
             if (_cachedConfig != null)
@@ -56,17 +94,7 @@ namespace TransmissionRssManager.Services
 
         public async Task SaveConfigAsync(AppConfig config)
         {
-            try
+            await SaveConfigurationAsync(config);
-            {
-                _cachedConfig = config;
-                await SaveConfigToFileAsync(config);
-                _logger.LogInformation("Configuration saved successfully to file");
-            }
-            catch (Exception ex)
-            {
-                _logger.LogError(ex, "Error saving configuration to file");
-                throw;
-            }
         }
 
         public async Task<string> GetSettingAsync(string key, string defaultValue = "")
@@ -245,6 +273,46 @@ namespace TransmissionRssManager.Services
             }
         }
 
+        private AppConfig LoadConfigFromFileSync()
+        {
+            try
+            {
+                if (!File.Exists(_configFilePath))
+                {
+                    _logger.LogWarning($"Configuration file not found at {_configFilePath}, creating default config");
+                    var defaultConfig = CreateDefaultConfig();
+                    // Save synchronously since we're in a sync method
+                    File.WriteAllText(_configFilePath, JsonSerializer.Serialize(defaultConfig, new JsonSerializerOptions
+                    {
+                        WriteIndented = true,
+                        PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+                    }));
+                    return defaultConfig;
+                }
+
+                string json = File.ReadAllText(_configFilePath);
+                var config = JsonSerializer.Deserialize<AppConfig>(json, new JsonSerializerOptions 
+                { 
+                    PropertyNameCaseInsensitive = true 
+                });
+
+                if (config == null)
+                {
+                    throw new InvalidOperationException("Failed to deserialize configuration");
+                }
+                
+                // Fill in any missing values with defaults
+                EnsureCompleteConfig(config);
+                
+                return config;
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Error loading configuration from file");
+                throw;
+            }
+        }
+
         private async Task<AppConfig> LoadConfigFromFileAsync()
         {
             try

src/Services/LoggingService.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -44,7 +46,7 @@ namespace TransmissionRssManager.Services
         Task<List<LogEntry>> GetLogsAsync(LogFilterOptions options);
         Task ClearLogsAsync(DateTime? olderThan = null);
         Task<byte[]> ExportLogsAsync(LogFilterOptions options);
-        void Log(LogLevel level, string message, string context = null, Dictionary<string, string> properties = null);
+        void Log(LogLevel level, string message, string? context = null, Dictionary<string, string>? properties = null);
     }
 
     public class LogFilterOptions
@@ -166,7 +168,7 @@ namespace TransmissionRssManager.Services
             return Encoding.UTF8.GetBytes(json);
         }
 
-        public void Log(LogLevel level, string message, string context = null, Dictionary<string, string> properties = null)
+        public void Log(LogLevel level, string message, string? context = null, Dictionary<string, string>? properties = null)
         {
             var levelString = level.ToString();