Postgres perf, path migration, and shutdown race fixes

- Major query performance boost: replaced correlated subqueries with DistinctBy() in BaseItemRepository, added episode deduplication index, and increased default command timeout to 120s.
- Fixed LibraryMonitor shutdown race: added disposal checks and exception handling in FileRefresher to prevent ObjectDisposedException.
- Added PowerShell and SQL utilities for fixing Linux paths in config files and database; new scripts for WebDir and path migration.
- Auto-fix for WebDir in startup.json on load; new helper scripts and docs.
- Added automated weekly DB performance monitoring scripts and reporting.
- Expanded documentation and README for all fixes, scripts, and migration steps.
- Updated SQL scripts for index creation and diagnostics; improved output handling.
- Updated db-config defaults and added new diagnostic/report files.

Emby.Server.Implementations/IO/FileRefresher.cs

@@ -109,6 +109,12 @@ namespace Emby.Server.Implementations.IO
 
         private void OnTimerCallback(object? state)
         {
+            // Check if disposed before processing
+            if (_disposed)
+            {
+                return;
+            }
+
             List<string> paths;
 
             lock (_timerLock)
@@ -121,6 +127,12 @@ namespace Emby.Server.Implementations.IO
             DisposeTimer();
             Completed?.Invoke(this, EventArgs.Empty);
 
+            // Double-check disposal after timer is disposed
+            if (_disposed)
+            {
+                return;
+            }
+
             try
             {
                 ProcessPathChanges(paths);
@@ -133,11 +145,28 @@ namespace Emby.Server.Implementations.IO
 
         private void ProcessPathChanges(List<string> paths)
         {
-            IEnumerable<BaseItem> itemsToRefresh = paths
-                .Distinct()
-                .Select(GetAffectedBaseItem)
-                .Where(item => item is not null)
-                .DistinctBy(x => x!.Id)!;  // Removed null values in the previous .Where()
+            // Check if disposed before accessing services
+            if (_disposed)
+            {
+                return;
+            }
+
+            IEnumerable<BaseItem> itemsToRefresh;
+
+            try
+            {
+                itemsToRefresh = paths
+                    .Distinct()
+                    .Select(GetAffectedBaseItem)
+                    .Where(item => item is not null)
+                    .DistinctBy(x => x!.Id)!;  // Removed null values in the previous .Where()
+            }
+            catch (ObjectDisposedException)
+            {
+                // Service provider has been disposed during shutdown, skip processing
+                _logger.LogDebug("Service provider disposed during path change processing, skipping refresh");
+                return;
+            }
 
             foreach (var item in itemsToRefresh)
             {