add global mutex to ensure single instance (#1324)

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
+### Fixed
+- Only allow a single instance of ErsatzTV to run
+  - This fixes some cases where the search index would become unusable
 
 ## [0.8.0-beta] - 2023-06-23
 ### Added

ErsatzTV/Program.cs

@@ -43,6 +43,13 @@ public class Program
 
     public static async Task<int> Main(string[] args)
     {
+        using var _ = new Mutex(true, "Global\\ErsatzTV.Singleton.74360cd8985c4d1fb6bc9e81887206fe", out bool createdNew);
+        if (!createdNew)
+        {
+            Console.WriteLine("Another instance of ErsatztTV is already running.");
+            return 1;
+        }
+
         LoggingLevelSwitch.MinimumLevel = LogEventLevel.Information;
 
         LoggerConfiguration loggerConfiguration = new LoggerConfiguration()