SQLite Hangfire (#1488)

* Update to use SQLIte for Hangfire to retain information on tasks

* Updated all external links to have noopener noreferrer

* When watching folders, ensure the folders exist before creating watchers.

* Tweaked the messaging for Email Service and added link to the project.

API/Startup.cs

@@ -17,6 +17,7 @@ using API.Services.Tasks;
 using API.SignalR;
 using Hangfire;
 using Hangfire.MemoryStorage;
+using Hangfire.Storage.SQLite;
 using Kavita.Common;
 using Kavita.Common.EnvironmentInfo;
 using Microsoft.AspNetCore.Builder;
@@ -155,7 +156,7 @@ namespace API
             services.AddHangfire(configuration => configuration
                 .UseSimpleAssemblyNameTypeSerializer()
                 .UseRecommendedSerializerSettings()
-                .UseMemoryStorage());
+                .UseSQLiteStorage());
 
             // Add the processing server as IHostedService
             services.AddHangfireServer(options =>