feat(data): rename *.Services projects, lift TrackEntity onto BlazorBlocks data layer, regenerate initial Postgres migration

DeepDrftWeb.Services → DeepDrftData; DeepDrftContent.Services → DeepDrftContent.Data.
TrackEntity:BaseEntity, TrackRepository:Repository<>, TrackManager:Manager<>+ITrackService.
Drops DeepDrftModels PagingParameters/PagedResult in favour of Models.Common.* from BlazorBlocks.
InitialCreate migration captures full schema including is_deleted index.

DeepDrftContent.Data/FileDatabase/Models/MetaData.cs

@@ -0,0 +1,33 @@
+using System.Text.Json.Serialization;
+
+namespace DeepDrftContent.Data.FileDatabase.Models;
+
+/// <summary>
+/// Base metadata for media entries
+/// </summary>
+/// <param name="MediaKey">The key used to identify the media file</param>
+/// <param name="Extension">The file extension of the media</param>
+[JsonPolymorphic(TypeDiscriminatorPropertyName = "$type")]
+[JsonDerivedType(typeof(MetaData), typeDiscriminator: "media")]
+[JsonDerivedType(typeof(ImageMetaData), typeDiscriminator: "image")]
+[JsonDerivedType(typeof(AudioMetaData), typeDiscriminator: "audio")]
+public record MetaData(string MediaKey, string Extension);
+
+/// <summary>
+/// Extended metadata for image entries, including aspect ratio
+/// </summary>
+/// <param name="MediaKey">The key used to identify the media file</param>
+/// <param name="Extension">The file extension of the media</param>
+/// <param name="AspectRatio">The aspect ratio of the image</param>
+public record ImageMetaData(string MediaKey, string Extension, double AspectRatio) 
+    : MetaData(MediaKey, Extension);
+
+/// <summary>
+/// Extended metadata for audio entries, including duration and bitrate
+/// </summary>
+/// <param name="MediaKey">The key used to identify the media file</param>
+/// <param name="Extension">The file extension of the media</param>
+/// <param name="Duration">The duration of the audio in seconds</param>
+/// <param name="Bitrate">The bitrate of the audio in kbps</param>
+public record AudioMetaData(string MediaKey, string Extension, double Duration, int Bitrate) 
+    : MetaData(MediaKey, Extension);