Integrate PostgreSQL with EF Core & migrations

Add PostgreSQL support and EF Core migrations for local development. Introduces ApplicationDbContext, adds Npgsql.EntityFrameworkCore.PostgreSQL and EF Core Design packages, and includes generated migrations (InitialPostgres and RemoveTestItems) plus updated model snapshot. Program.cs now loads an optional API/appsettings.custom.json, configures the DbContext from ConnectionStrings:Postgres and runs Database.Migrate() on startup. Adds a Dev docker-compose.yml to run postgres + pgAdmin, pins dotnet-ef in dotnet-tools.json, and adds ConnectionStrings to appsettings files. Also ignores API/appsettings.custom.json in .gitignore and updates README/codexInfo to document the new DB/dev workflow.

API/Migrations/20260418134949_InitialPostgres.Designer.cs

@@ -0,0 +1,58 @@
+// <auto-generated />
+using System;
+using API.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace API.Migrations
+{
+    [DbContext(typeof(ApplicationDbContext))]
+    [Migration("20260418134949_InitialPostgres")]
+    partial class InitialPostgres
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.4")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("API.Models.Test.TestItem", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<DateTime>("CreatedAtUtc")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Description")
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<DateTime>("UpdatedAtUtc")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("test_items", (string)null);
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

API/Migrations/20260418134949_InitialPostgres.cs

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+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace API.Migrations
+{
+    /// <inheritdoc />
+    public partial class InitialPostgres : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "test_items",
+                columns: table => new
+                {
+                    Id = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    Name = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    Description = table.Column<string>(type: "character varying(2000)", maxLength: 2000, nullable: true),
+                    CreatedAtUtc = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    UpdatedAtUtc = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_test_items", x => x.Id);
+                });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "test_items");
+        }
+    }
+}

API/Migrations/20260418153650_RemoveTestItems.Designer.cs

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+// <auto-generated />
+using API.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace API.Migrations
+{
+    [DbContext(typeof(ApplicationDbContext))]
+    [Migration("20260418153650_RemoveTestItems")]
+    partial class RemoveTestItems
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.4")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+#pragma warning restore 612, 618
+        }
+    }
+}

API/Migrations/20260418153650_RemoveTestItems.cs

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+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace API.Migrations
+{
+    /// <inheritdoc />
+    public partial class RemoveTestItems : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "test_items");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "test_items",
+                columns: table => new
+                {
+                    Id = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    CreatedAtUtc = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    Description = table.Column<string>(type: "character varying(2000)", maxLength: 2000, nullable: true),
+                    Name = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    UpdatedAtUtc = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_test_items", x => x.Id);
+                });
+        }
+    }
+}

API/Migrations/ApplicationDbContextModelSnapshot.cs

@@ -0,0 +1,26 @@
+// <auto-generated />
+using API.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace API.Migrations
+{
+    [DbContext(typeof(ApplicationDbContext))]
+    partial class ApplicationDbContextModelSnapshot : ModelSnapshot
+    {
+        protected override void BuildModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.4")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+#pragma warning restore 612, 618
+        }
+    }
+}