feat: normalize subscription architecture, integrate pgvector, and implement Stripe webhook subscription management.

src/NexusReader.Infrastructure/Persistence/AppDbContextFactory.cs

@@ -0,0 +1,45 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Design;
+using Microsoft.Extensions.Configuration;
+using Pgvector.EntityFrameworkCore;
+
+namespace NexusReader.Infrastructure.Persistence;
+
+public class AppDbContextFactory : IDesignTimeDbContextFactory<AppDbContext>
+{
+    public AppDbContext CreateDbContext(string[] args)
+    {
+        var environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Development";
+        
+        // Try to find the Web project directory by looking for the solution root
+        var currentDir = new DirectoryInfo(Directory.GetCurrentDirectory());
+        while (currentDir != null && !File.Exists(Path.Combine(currentDir.FullName, "NexusReader.slnx")))
+        {
+            currentDir = currentDir.Parent;
+        }
+
+        var basePath = currentDir != null 
+            ? Path.Combine(currentDir.FullName, "src", "NexusReader.Web.New")
+            : Directory.GetCurrentDirectory();
+
+        var configuration = new ConfigurationBuilder()
+            .SetBasePath(basePath)
+            .AddJsonFile("appsettings.json", optional: true)
+            .AddJsonFile($"appsettings.{environment}.json", optional: true)
+            .AddEnvironmentVariables()
+            .Build();
+
+        var optionsBuilder = new DbContextOptionsBuilder<AppDbContext>();
+        var connectionString = configuration.GetConnectionString("PostgresConnection");
+
+        if (string.IsNullOrEmpty(connectionString))
+        {
+             // For design time, if no PG connection is found, we might be using Sqlite or just testing
+             connectionString = "Host=localhost;Database=nexus_reader;Username=postgres;Password=postgres";
+        }
+
+        optionsBuilder.UseNpgsql(connectionString, x => x.UseVector());
+
+        return new AppDbContext(optionsBuilder.Options);
+    }
+}