feat: implement central package management and stabilize mobile build

src/NexusReader.Domain/Entities/SemanticKnowledgeCache.cs

@@ -1,5 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
+using Pgvector;
 
 namespace NexusReader.Domain.Entities;
 
@@ -27,5 +28,8 @@ public class SemanticKnowledgeCache
     [MaxLength(128)]
     public string TenantId { get; set; } = string.Empty;
 
+    // Vector embedding for semantic search (768 dimensions)
+    public Vector? Embedding { get; set; }
+
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 }