Initialize minimal ASP.NET Core API with OpenAPI support

Set up a basic ASP.NET Core project targeting .NET 9.0 with nullable and implicit usings enabled. Added OpenAPI (Swagger) documentation using NSwag and a simple WeatherForecast endpoint. Included necessary configuration files for development and toolchain support.

Api/Properties/launchSettings.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "http://localhost:5175",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "https://localhost:7081;http://localhost:5175",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}