feat(bff): add /health endpoint (refs #28)

Register ASP.NET Core health checks and map GET /health. The endpoint
returns 200 with a "Healthy" body by default, making the red test pass.
Smallest change to go green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/bff/Bff.Api/Program.cs

@@ -1,7 +1,10 @@
 var builder = WebApplication.CreateBuilder(args);
+builder.Services.AddHealthChecks();
+
 var app = builder.Build();
 
 app.MapGet("/", () => "BFF placeholder");
+app.MapHealthChecks("/health");
 
 app.Run();
 

services/bff/Bff.Api/Properties/launchSettings.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "applicationUrl": "http://localhost:5249",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "applicationUrl": "https://localhost:7106;http://localhost:5249",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

services/bff/Bff.Api/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

services/bff/Bff.Api/appsettings.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}