Serve SPA from API and add health endpoint

Switch backend to serve the built SPA and static assets, add a minimal health endpoint, and clean up template code. Changes: added API/Controllers/HealthController.cs (GET /api/health -> 200), removed WeatherForecast controller and model, removed OpenAPI package reference and OpenAPI wiring from API.csproj/Program.cs, updated Program.cs to serve wwwroot with default files/static files and a SPA fallback that returns index.html for non-/api routes (/api/* returns 404), updated GUI/vite.config.ts to output build to API/wwwroot and clear the directory, added API/wwwroot to .gitignore, and updated codexInfo.md to document these changes. This enables the GUI build to be deployed directly into the API project and served as a single-page app.

API/Controllers/HealthController.cs

@@ -0,0 +1,14 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace API.Controllers;
+
+[ApiController]
+[Route("api/health")]
+public class HealthController : ControllerBase
+{
+    [HttpGet]
+    public IActionResult Get()
+    {
+        return Ok();
+    }
+}

API/Controllers/WeatherForecastController.cs

@@ -1,26 +0,0 @@
-using Microsoft.AspNetCore.Mvc;
-
-namespace API.Controllers
-{
-    [ApiController]
-    [Route("[controller]")]
-    public class WeatherForecastController : ControllerBase
-    {
-        private static readonly string[] Summaries =
-        [
-            "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
-        ];
-
-        [HttpGet(Name = "GetWeatherForecast")]
-        public IEnumerable<WeatherForecast> Get()
-        {
-            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
-            {
-                Date = DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
-                TemperatureC = Random.Shared.Next(-20, 55),
-                Summary = Summaries[Random.Shared.Next(Summaries.Length)]
-            })
-            .ToArray();
-        }
-    }
-}