Refactor database configuration and migrations for PostgreSQL support

- Updated default database configuration to use PostgreSQL instead of SQLite when no database.xml exists.
- Removed obsolete migration routines: MigrateUserDb, RemoveDuplicateExtras, ReseedFolderFlag.
- Introduced new read-only view projections for PostgreSQL: ItemPersonView, ItemProviderView, LibrarySummaryView, MediaStreamInfoView, UserPlaybackHistoryView, VideoItemView.
- Registered view mappings in PostgresDatabaseProvider to ensure proper handling of read-only views.
- Cleaned up unused SQLite cache size configuration in ConfigurationExtensions.

Co-authored-by: Copilot <copilot@github.com>

MediaBrowser.Controller/Extensions/ConfigurationExtensions.cs

@@ -68,11 +68,6 @@ namespace MediaBrowser.Controller.Extensions
         /// </summary>
         public const string UnixSocketPermissionsKey = "kestrel:socketPermissions";
 
-        /// <summary>
-        /// The cache size of the SQL database, see cache_size.
-        /// </summary>
-        public const string SqliteCacheSizeKey = "sqlite:cacheSize";
-
         /// <summary>
         /// The key for a setting that indicates whether the application should detect network status change.
         /// </summary>
@@ -143,12 +138,5 @@ namespace MediaBrowser.Controller.Extensions
         public static string? GetUnixSocketPermissions(this IConfiguration configuration)
             => configuration[UnixSocketPermissionsKey];
 
-        /// <summary>
-        /// Gets the cache_size from the <see cref="IConfiguration" />.
-        /// </summary>
-        /// <param name="configuration">The configuration to read the setting from.</param>
-        /// <returns>The sqlite cache size.</returns>
-        public static int? GetSqliteCacheSize(this IConfiguration configuration)
-            => configuration.GetValue<int?>(SqliteCacheSizeKey);
     }
 }