Refactor downloads to use job-specific subdirectories

Organize downloaded files into per-job subdirectories under "downloads" instead of a flat structure. Update DownloadController and VideoService to read, write, and delete files within these job-specific directories. Add helper methods for directory management and improve logging. Update download/delete endpoints and result URLs to reflect the new structure. Clean up empty job directories after file deletion.

TuneRipper.Api/Program.cs

@@ -10,6 +10,7 @@ builder.Services.AddHttpClient();
 
 // Register services
 builder.Services.AddScoped<IVideoService, VideoService>();
+builder.Services.AddSingleton<ISessionService, SessionService>(); // Register session service as singleton
 
 // Add CORS for Blazor WebAssembly client
 builder.Services.AddCors(options =>
@@ -64,6 +65,7 @@ app.MapGet("/", (IWebHostEnvironment env) => new
         check_status = "/api/video/status/{jobId}",
         get_result = "/api/video/result/{jobId}",
         download = "/api/download/{jobId}",
+        download_by_session = "/api/download/{sessionId}/{jobId}",
         static_files = "/downloads/{fileName}",
         openapi = "/openapi/v1.json"
     },
@@ -80,10 +82,11 @@ app.MapControllers();
 app.Logger.LogInformation("?? TuneRipper API is starting...");
 app.Logger.LogInformation("?? Environment: {Environment}", app.Environment.EnvironmentName);
 app.Logger.LogInformation("?? API will be available at:");
-app.Logger.LogInformation("   • HTTPS: https://localhost:7160");
-app.Logger.LogInformation("   • HTTP: http://localhost:5112");
+app.Logger.LogInformation("   ?? HTTPS: https://localhost:7160");
+app.Logger.LogInformation("   ?? HTTP: http://localhost:5112");
 app.Logger.LogInformation("?? Health check: /api/health");
 app.Logger.LogInformation("?? API info: /");
 app.Logger.LogInformation("?? Static files served from: /downloads/*");
+app.Logger.LogInformation("?? Session-based downloads supported");
 
 app.Run();