Add "Download All in ZIP" feature for session downloads

Introduce automatic ZIP file creation and management for session-based downloads.
- Server: Add endpoints to serve and provide info about session ZIPs; VideoService now updates ZIP after each MP3 download with user-friendly filenames.
- Client: Add "Download All in ZIP" button with loading state and ZIP info; trigger browser download via JS interop; responsive and styled UI.
- API: Extend service interfaces for ZIP download/info; add SessionZipInfo model.
- Docs: Update SESSION_MANAGEMENT.md with ZIP workflow, endpoints, and UX details.
- Robust error handling and logging throughout.

TuneRipper.Api/Services/VideoService.cs

@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using System.Text.RegularExpressions;
 using System.Diagnostics;
 using System.Text;
+using System.IO.Compression;
 
 namespace TuneRipper.Api.Services;
 
@@ -206,6 +207,9 @@ public class VideoService : IVideoService
             
             _logger.LogInformation("Successfully processed video. Job: {JobId}, Session: {SessionId}, File: {FileName}", jobId, sessionId, finalFileName);
             
+            // Update the session ZIP file after successful download
+            await UpdateSessionZipAsync(sessionId, downloadDir);
+            
             progressCallback(100, "Processing completed successfully");
             
             return finalFileName;
@@ -218,6 +222,93 @@ public class VideoService : IVideoService
         }
     }
 
+    private async Task UpdateSessionZipAsync(string sessionId, string sessionDir)
+    {
+        try
+        {
+            var zipFileName = $"session_{sessionId}.zip";
+            var zipFilePath = Path.Combine(sessionDir, zipFileName);
+            
+            // Get all MP3 files in the session directory
+            var mp3Files = Directory.GetFiles(sessionDir, "*.mp3")
+                .Where(f => !f.EndsWith(zipFileName)) // Exclude the ZIP file itself
+                .ToArray();
+
+            if (mp3Files.Length == 0)
+            {
+                _logger.LogWarning("No MP3 files found to add to ZIP for session: {SessionId}", sessionId);
+                return;
+            }
+
+            // Delete existing ZIP file if it exists
+            if (File.Exists(zipFilePath))
+            {
+                File.Delete(zipFilePath);
+            }
+
+            // Create new ZIP file with all MP3 files
+            using (var archive = ZipFile.Open(zipFilePath, ZipArchiveMode.Create))
+            {
+                foreach (var mp3File in mp3Files)
+                {
+                    var fileName = Path.GetFileName(mp3File);
+                    
+                    // Create user-friendly filename for ZIP entry
+                    var friendlyFileName = CreateUserFriendlyFileName(fileName);
+                    
+                    // Add file to ZIP
+                    archive.CreateEntryFromFile(mp3File, friendlyFileName);
+                }
+            }
+
+            _logger.LogInformation("Updated session ZIP file: {ZipFile} with {Count} MP3 files for session: {SessionId}", 
+                zipFileName, mp3Files.Length, sessionId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error updating session ZIP file for session: {SessionId}", sessionId);
+            // Don't throw - ZIP creation failure shouldn't break the main process
+        }
+    }
+
+    private string CreateUserFriendlyFileName(string originalFileName)
+    {
+        try
+        {
+            // Parse our pattern: jobId_title.ext
+            var nameWithoutExt = Path.GetFileNameWithoutExtension(originalFileName);
+            var extension = Path.GetExtension(originalFileName);
+            
+            // Split by underscore - first part is job ID, rest is title
+            var underscoreIndex = nameWithoutExt.IndexOf('_');
+            
+            if (underscoreIndex > 0 && underscoreIndex < nameWithoutExt.Length - 1)
+            {
+                // Extract title part (everything after the first underscore)
+                var titlePart = nameWithoutExt.Substring(underscoreIndex + 1);
+                
+                // Convert underscores back to spaces in title
+                var friendlyTitle = titlePart.Replace("_", " ");
+                
+                // Create a clean filename: "Title.mp3"
+                if (friendlyTitle.Length > 0)
+                {
+                    // Remove any duplicate spaces and clean up
+                    friendlyTitle = System.Text.RegularExpressions.Regex.Replace(friendlyTitle, @"\s+", " ").Trim();
+                    return $"{friendlyTitle}{extension}";
+                }
+            }
+            
+            // Fallback to original filename if pattern doesn't match
+            return originalFileName;
+        }
+        catch (Exception)
+        {
+            // If anything goes wrong, return the original filename
+            return originalFileName;
+        }
+    }
+
     private string SanitizeFileName(string fileName)
     {
         if (string.IsNullOrWhiteSpace(fileName))