Remove /api prefix from all routes and fix CityId FK constraint

- Strip /api prefix from all endpoint routes
- Make Show.CityId nullable (no longer required FK)
- Drop CityId FK constraint and alter column to NULL at startup via raw SQL
- Add migration MakeCityIdNullable for schema consistency
- Update Show DTOs to reflect nullable CityId

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

PyroFetes/Migrations/20260527000000_MakeCityIdNullable.cs

@@ -0,0 +1,59 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace PyroFetes.Migrations
+{
+    /// <inheritdoc />
+    public partial class MakeCityIdNullable : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Shows_Cities_CityId",
+                table: "Shows");
+
+            migrationBuilder.AlterColumn<int>(
+                name: "CityId",
+                table: "Shows",
+                type: "int",
+                nullable: true,
+                oldClrType: typeof(int),
+                oldType: "int");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Shows_Cities_CityId",
+                table: "Shows",
+                column: "CityId",
+                principalTable: "Cities",
+                principalColumn: "Id");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Shows_Cities_CityId",
+                table: "Shows");
+
+            migrationBuilder.AlterColumn<int>(
+                name: "CityId",
+                table: "Shows",
+                type: "int",
+                nullable: false,
+                defaultValue: 0,
+                oldClrType: typeof(int),
+                oldType: "int",
+                oldNullable: true);
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Shows_Cities_CityId",
+                table: "Shows",
+                column: "CityId",
+                principalTable: "Cities",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.Cascade);
+        }
+    }
+}

PyroFetes/Migrations/PyroFetesDbContextModelSnapshot.cs

@@ -813,7 +813,7 @@ namespace PyroFetes.Migrations
 
                     SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
 
-                    b.Property<int>("CityId")
+                    b.Property<int?>("CityId")
                         .HasColumnType("int");
 
                     b.Property<DateOnly?>("Date")
@@ -1594,8 +1594,7 @@ namespace PyroFetes.Migrations
                     b.HasOne("PyroFetes.Models.City", "City")
                         .WithMany("Shows")
                         .HasForeignKey("CityId")
-                        .OnDelete(DeleteBehavior.Cascade)
-                        .IsRequired();
+                        .OnDelete(DeleteBehavior.ClientSetNull);
 
                     b.Navigation("City");
                 });