refactor(api): consolidate health check endpoints to /health

Removes the redundant `/healthz` and `/api/v1/health` endpoints, leaving `/health` as the sole health check endpoint.

- Update router to return 404 Not Found for the removed endpoints
- Update admin log filtering to only ignore `/health`
- Remove health URL from API documentation data
- Update tests to verify `/health` returns 200 and others return 404
- Update README documentation to reflect the change

backend/libs/handlers/health_test.go

@@ -13,16 +13,20 @@ func TestHealthRoutes(t *testing.T) {
 	mux := http.NewServeMux()
 	app.RegisterRoutes(mux)
 
-	for _, path := range []string{"/health", "/healthz", "/api/v1/health"} {
-		t.Run(path, func(t *testing.T) {
-			request := httptest.NewRequest(http.MethodGet, path, nil)
-			response := httptest.NewRecorder()
+	request := httptest.NewRequest(http.MethodGet, "/health", nil)
+	response := httptest.NewRecorder()
 
-			mux.ServeHTTP(response, request)
+	mux.ServeHTTP(response, request)
 
-			if response.Code != http.StatusOK {
-				t.Fatalf("status = %d, body = %s", response.Code, response.Body.String())
-			}
-		})
+	if response.Code != http.StatusOK {
+		t.Fatalf("status = %d, body = %s", response.Code, response.Body.String())
+	}
+	for _, path := range []string{"/healthz", "/api/v1/health"} {
+		request := httptest.NewRequest(http.MethodGet, path, nil)
+		response := httptest.NewRecorder()
+		mux.ServeHTTP(response, request)
+		if response.Code != http.StatusNotFound {
+			t.Fatalf("%s status = %d, want 404", path, response.Code)
+		}
 	}
 }