Update config file logic and unify webDir path to wwwroot

- Prevent overwriting existing config files by only copying example files if the target does not exist.
- Set webDir to "wwwroot" for all OSes for consistency.
- Update last used publish profile to SelfContained-Win-x64.

Jellyfin.Server/Helpers/StartupHelpers.cs

@@ -138,7 +138,7 @@ public static class StartupHelpers
                 cacheDir = "C:/ProgramData/jellyfin/cache";
                 logDir = "C:/ProgramData/jellyfin/log";
                 tempDir = Path.Combine(Path.GetTempPath(), "jellyfin");
-                webDir = "C:/ProgramData/jellyfin/wwwroot";
+                webDir = "wwwroot";
                 osComment = "Windows defaults - using C:/ProgramData/jellyfin";
             }
             else if (OperatingSystem.IsLinux())
@@ -149,7 +149,7 @@ public static class StartupHelpers
                 cacheDir = "/var/cache/jellyfin";
                 logDir = "/var/log/jellyfin";
                 tempDir = "/var/tmp/jellyfin";
-                webDir = "/usr/share/jellyfin/wwwroot";
+                webDir = "wwwroot";
                 osComment = "Linux defaults - following Filesystem Hierarchy Standard (FHS)";
             }
             else if (OperatingSystem.IsMacOS())
@@ -161,7 +161,7 @@ public static class StartupHelpers
                 cacheDir = Path.Combine(homeDir, "Library", "Caches", "jellyfin");
                 logDir = Path.Combine(homeDir, "Library", "Logs", "jellyfin");
                 tempDir = Path.Combine(Path.GetTempPath(), "jellyfin");
-                webDir = Path.Combine(homeDir, "Library", "Application Support", "jellyfin", "wwwroot");
+                webDir = "wwwroot";
                 osComment = "macOS defaults - using user Library paths";
             }
             else