Refactor Docker setup to integrate Web UI and streamline configuration

- Updated Dockerfile to build and embed the SvelteKit Web UI directly into the gateway image, eliminating the need for a separate web service.
- Modified .dockerignore to exclude unnecessary directories related to the web service.
- Adjusted config.compose.yaml to remove CORS settings for the web service, as the UI now shares the same origin as the API.
- Enhanced README.md to reflect the new single-port architecture for accessing both the Web UI and API.
- Removed the standalone web Dockerfile and updated related documentation for local development and build processes.

internal/webui/handler_test.go

@@ -0,0 +1,28 @@
+package webui
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestHandler_index(t *testing.T) {
+	h := Handler()
+	rr := httptest.NewRecorder()
+	h.ServeHTTP(rr, httptest.NewRequest(http.MethodGet, "/", nil))
+	if rr.Code != http.StatusOK {
+		t.Fatalf("GET /: %d", rr.Code)
+	}
+	if got := rr.Header().Get("Content-Type"); got == "" {
+		t.Fatal("missing Content-Type")
+	}
+}
+
+func TestHandler_spaFallback(t *testing.T) {
+	h := Handler()
+	rr := httptest.NewRecorder()
+	h.ServeHTTP(rr, httptest.NewRequest(http.MethodGet, "/servers/foo", nil))
+	if rr.Code != http.StatusOK {
+		t.Fatalf("GET /servers/foo: %d", rr.Code)
+	}
+}