feat: complete mealplanner app (backend + frontend + deployment)

.NET 8 backend with Zitadel JWT auth, TheMealDB integration,
weekly meal plan generation, shopping list aggregation.
Vue 3 + Tailwind 4 frontend with dark emerald theme,
manual OIDC PKCE auth, all views implemented.
Multi-stage Dockerfile with nginx reverse proxy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/appsettings.json

@@ -0,0 +1,16 @@
+{
+  "ConnectionStrings": {
+    "DefaultConnection": "Host=localhost;Port=54320;Database=mealplanner;Username=mika;Password=changeme"
+  },
+  "Zitadel": {
+    "Issuer": "https://auth.kuns.dev",
+    "ClientId": ""
+  },
+  "AllowedOrigin": "https://essen.kuns.dev",
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.EntityFrameworkCore": "Warning"
+    }
+  }
+}