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/Controllers/SessionController.cs

@@ -0,0 +1,79 @@
+using Microsoft.AspNetCore.Mvc;
+using TuneRipper.Api.Services;
+
+namespace TuneRipper.Api.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+public class SessionController : ControllerBase
+{
+    private readonly ISessionService _sessionService;
+    private readonly ILogger<SessionController> _logger;
+
+    public SessionController(ISessionService sessionService, ILogger<SessionController> logger)
+    {
+        _sessionService = sessionService;
+        _logger = logger;
+    }
+
+    [HttpPost("create")]
+    public ActionResult<object> CreateSession()
+    {
+        try
+        {
+            var sessionId = _sessionService.CreateSession();
+            
+            return Ok(new
+            {
+                sessionId,
+                message = "Session created successfully",
+                expiresAt = DateTime.UtcNow.AddHours(24)
+            });
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error creating session");
+            return StatusCode(500, "Error creating session");
+        }
+    }
+
+    [HttpGet("validate/{sessionId}")]
+    public ActionResult<object> ValidateSession(string sessionId)
+    {
+        if (string.IsNullOrWhiteSpace(sessionId))
+        {
+            return BadRequest("Session ID is required");
+        }
+
+        var isValid = _sessionService.IsValidSession(sessionId);
+        
+        return Ok(new
+        {
+            sessionId,
+            isValid,
+            message = isValid ? "Session is valid" : "Session is invalid or expired"
+        });
+    }
+
+    [HttpPost("refresh/{sessionId}")]
+    public ActionResult<object> RefreshSession(string sessionId)
+    {
+        if (string.IsNullOrWhiteSpace(sessionId))
+        {
+            return BadRequest("Session ID is required");
+        }
+
+        if (!_sessionService.IsValidSession(sessionId))
+        {
+            return NotFound("Session not found or expired");
+        }
+
+        // Session is automatically refreshed when IsValidSession is called
+        return Ok(new
+        {
+            sessionId,
+            message = "Session refreshed successfully",
+            expiresAt = DateTime.UtcNow.AddHours(24)
+        });
+    }
+}