Add automatic PostgreSQL database creation and migration

- Added Jellyfin.Database.Providers.Postgres project with full EF Core migration support for PostgreSQL.
- Implemented automatic database creation and privilege assignment on startup.
- Generated initial migration and model snapshot for PostgreSQL schema.
- Updated build, test, and dependency files to include PostgreSQL provider and Npgsql packages.
- Added PowerShell script for generating and testing PostgreSQL migrations.
- No changes to application logic outside database provider/migration infrastructure.

Jellyfin.Server.Implementations/obj/project.nuget.cache

@@ -1,6 +1,6 @@
 {
   "version": 2,
-  "dgSpecHash": "2uqnqkg9VpI=",
+  "dgSpecHash": "q38UsTgstaw=",
   "success": true,
   "projectFilePath": "E:\\Projects\\pgsql-jellyfin\\Jellyfin.Server.Implementations\\Jellyfin.Server.Implementations.csproj",
   "expectedPackageFiles": [
@@ -39,6 +39,8 @@
     "C:\\Users\\wjones\\.nuget\\packages\\microsoft.kiota.serialization.multipart\\1.20.1\\microsoft.kiota.serialization.multipart.1.20.1.nupkg.sha512",
     "C:\\Users\\wjones\\.nuget\\packages\\microsoft.kiota.serialization.text\\1.20.1\\microsoft.kiota.serialization.text.1.20.1.nupkg.sha512",
     "C:\\Users\\wjones\\.nuget\\packages\\nebml\\1.1.0.5\\nebml.1.1.0.5.nupkg.sha512",
+    "C:\\Users\\wjones\\.nuget\\packages\\npgsql\\10.0.0\\npgsql.10.0.0.nupkg.sha512",
+    "C:\\Users\\wjones\\.nuget\\packages\\npgsql.entityframeworkcore.postgresql\\11.0.0-preview.1\\npgsql.entityframeworkcore.postgresql.11.0.0-preview.1.nupkg.sha512",
     "C:\\Users\\wjones\\.nuget\\packages\\polly\\8.6.5\\polly.8.6.5.nupkg.sha512",
     "C:\\Users\\wjones\\.nuget\\packages\\polly.core\\8.6.5\\polly.core.8.6.5.nupkg.sha512",
     "C:\\Users\\wjones\\.nuget\\packages\\seriloganalyzer\\0.15.0\\seriloganalyzer.0.15.0.nupkg.sha512",