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/IIndex.cs

@@ -0,0 +1,66 @@
+namespace DeepDrftContent.Data.FileDatabase.Models;
+
+/// <summary>
+/// Base interface for all index types - minimal contract
+/// </summary>
+public interface IIndex
+{
+    /// <summary>
+    /// Gets the key identifier for this index
+    /// </summary>
+    string GetKey();
+}
+
+/// <summary>
+/// Interface for indexes that support entry queries
+/// </summary>
+public interface IEntryQueryable : IIndex
+{
+    /// <summary>
+    /// Gets all entry IDs in this index
+    /// </summary>
+    IReadOnlyList<string> GetEntries();
+
+    /// <summary>
+    /// Gets the number of entries in this index
+    /// </summary>
+    int GetEntriesSize();
+
+    /// <summary>
+    /// Checks if the index contains the specified entry ID
+    /// </summary>
+    bool HasEntry(string entryId);
+}
+
+/// <summary>
+/// Interface for indexes that support directory operations
+/// </summary>
+public interface IDirectoryIndex : IEntryQueryable
+{
+    /// <summary>
+    /// Adds an entry to the directory index
+    /// </summary>
+    void PutEntry(string entryId);
+}
+
+/// <summary>
+/// Interface for indexes that support vault operations with metadata
+/// </summary>
+public interface IVaultIndex : IEntryQueryable
+{
+    /// <summary>
+    /// Gets metadata for a specific entry
+    /// </summary>
+    MetaData? GetEntry(string entryId);
+
+    /// <summary>
+    /// Adds an entry with metadata to the vault index
+    /// </summary>
+    void PutEntry(string entryId, MetaData metaData);
+
+    /// <summary>
+    /// Removes an entry (and its metadata) from the vault index.
+    /// Returns true if an entry was removed, false if it was not present.
+    /// </summary>
+    bool RemoveEntry(string entryId);
+}