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.

sql/fix_windows_paths.sql

@@ -0,0 +1,146 @@
+-- PostgreSQL Path Fix for Windows
+-- This script converts Linux paths stored in the database to Windows paths
+-- Run this if you migrated from Linux or have incorrect paths in your database
+\pset pager off
+
+-- IMPORTANT: Backup your database before running this script!
+
+-- Step 1: Check what paths exist in your database
+SELECT 'ImageInfo Paths' AS table_name, COUNT(*) AS count, 
+       COUNT(CASE WHEN "Path" LIKE '/var/lib/jellyfin/%' THEN 1 END) AS linux_paths,
+       COUNT(CASE WHEN "Path" LIKE '/var/%' OR "Path" LIKE '/usr/%' THEN 1 END) AS all_linux_paths
+FROM library."ImageInfos"
+UNION ALL
+SELECT 'BaseItems Paths' AS table_name, COUNT(*) AS count,
+       COUNT(CASE WHEN "Path" LIKE '/var/lib/jellyfin/%' THEN 1 END) AS linux_paths,
+       COUNT(CASE WHEN "Path" LIKE '/var/%' OR "Path" LIKE '/usr/%' THEN 1 END) AS all_linux_paths
+FROM library."BaseItems";
+
+-- Step 2: Show sample paths that will be updated
+(SELECT '"ImageInfos"' AS table_name, "Id"::text, "Path" AS current_path
+FROM library."ImageInfos"
+WHERE "Path" LIKE '/var/lib/jellyfin/%' OR "Path" LIKE '/var/%' OR "Path" LIKE '/usr/%'
+LIMIT 10)
+UNION ALL
+(SELECT '"BaseItems"' AS table_name, "Id"::text, "Path" AS current_path
+FROM library."BaseItems"
+WHERE "Path" LIKE '/var/lib/jellyfin/%' OR "Path" LIKE '/var/%' OR "Path" LIKE '/usr/%'
+LIMIT 10);
+
+-- Step 3: Preview the path conversion (does NOT modify data)
+-- This shows you what the new paths will look like
+SELECT 
+    "Id",
+    "Path" AS old_path,
+    REGEXP_REPLACE(
+        REGEXP_REPLACE(
+            "Path",
+            '^/var/lib/jellyfin',
+            'C:/ProgramData/jellyfin/data',
+            'g'
+        ),
+        '/',
+        '\',
+        'g'
+    ) AS new_path
+FROM library."ImageInfos"
+WHERE "Path" LIKE '/var/lib/jellyfin/%'
+LIMIT 5;
+
+-- ===========================================================================
+-- STOP HERE AND REVIEW THE OUTPUT ABOVE BEFORE PROCEEDING!
+-- ===========================================================================
+-- If the preview looks correct, uncomment and run the UPDATE statements below
+
+/*
+-- Step 4: Update ImageInfo paths
+-- Convert: /var/lib/jellyfin -> C:/ProgramData/jellyfin/data
+-- Convert: / -> \
+BEGIN;
+
+UPDATE library."ImageInfos"
+SET "Path" = REGEXP_REPLACE(
+    REGEXP_REPLACE(
+        "Path",
+        '^/var/lib/jellyfin',
+        'C:/ProgramData/jellyfin/data',
+        'g'
+    ),
+    '/',
+    '\',
+    'g'
+)
+WHERE "Path" LIKE '/var/lib/jellyfin/%';
+
+-- Show how many rows were updated
+SELECT 'Updated ImageInfos: ' || ROW_COUNT() AS result;
+
+COMMIT;
+
+-- Step 5: Update BaseItems paths (if needed)
+BEGIN;
+
+UPDATE library."BaseItems"
+SET "Path" = REGEXP_REPLACE(
+    REGEXP_REPLACE(
+        "Path",
+        '^/var/lib/jellyfin',
+        'C:/ProgramData/jellyfin/data',
+        'g'
+    ),
+    '/',
+    '\',
+    'g'
+)
+WHERE "Path" LIKE '/var/lib/jellyfin/%';
+
+SELECT 'Updated BaseItems: ' || ROW_COUNT() AS result;
+
+COMMIT;
+
+-- Step 6: Update any other Linux paths (e.g., /usr/share/jellyfin)
+BEGIN;
+
+UPDATE library."BaseItems"
+SET "Path" = REGEXP_REPLACE(
+    REGEXP_REPLACE(
+        "Path",
+        '^/usr/share/jellyfin',
+        'C:/Program Files/Jellyfin',
+        'g'
+    ),
+    '/',
+    '\',
+    'g'
+)
+WHERE "Path" LIKE '/usr/share/jellyfin/%';
+
+SELECT 'Updated BaseItems (usr/share): ' || ROW_COUNT() AS result;
+
+COMMIT;
+
+-- Step 7: Verify the changes
+SELECT 'Verification - ImageInfos' AS check_type, 
+       COUNT(*) AS total_rows,
+       COUNT(CASE WHEN "Path" LIKE '/var/%' OR "Path" LIKE '/usr/%' THEN 1 END) AS remaining_linux_paths
+FROM library."ImageInfos"
+UNION ALL
+SELECT 'Verification - BaseItems' AS check_type,
+       COUNT(*) AS total_rows,
+       COUNT(CASE WHEN "Path" LIKE '/var/%' OR "Path" LIKE '/usr/%' THEN 1 END) AS remaining_linux_paths
+FROM library."BaseItems";
+
+*/
+
+-- ===========================================================================
+-- IMPORTANT NOTES:
+-- ===========================================================================
+-- 1. This script assumes your Windows Jellyfin data is at C:/ProgramData/jellyfin/data
+--    If it's different, update the path in the REGEXP_REPLACE statements
+-- 
+-- 2. The script converts forward slashes (/) to backslashes (\)
+--    However, .NET's Path class accepts forward slashes on Windows too
+--
+-- 3. You may need to restart Jellyfin after running this script
+--
+-- 4. If you have custom metadata paths, you'll need to adjust the script accordingly