feat: Add Kubernetes examples and update dependencies

- Add Kubernetes examples demonstrating deployment of various
  applications (PostgreSQL, Redis, generic). This improves the
  documentation and provides practical usage examples.
- Add `tokio` dependency for async examples. This enables the use
  of asynchronous operations in the examples.
- Add `once_cell` dependency for improved resource management in
  Kubernetes module. This allows efficient management of
  singletons and other resources.

kubernetes/tests/rhai/pod_env_vars_test.rhai

@@ -0,0 +1,142 @@
+// Rhai test for pod creation with environment variables functionality
+// This test verifies that the enhanced pod_create function works correctly with environment variables
+
+print("=== Testing Pod Environment Variables in Rhai ===");
+
+// Create Kubernetes manager
+print("Creating Kubernetes manager...");
+let km = kubernetes_manager_new("default");
+print("✓ Kubernetes manager created");
+
+// Test 1: Create pod with environment variables
+print("\n--- Test 1: Create Pod with Environment Variables ---");
+
+// Clean up any existing resources
+try {
+    delete_pod(km, "rhai-pod-env-test");
+    print("✓ Cleaned up existing pod");
+} catch(e) {
+    print("✓ No existing pod to clean up");
+}
+
+// Create pod with both labels and environment variables
+try {
+    let result = km.create_pod_with_env("rhai-pod-env-test", "nginx:latest", #{
+        "app": "rhai-pod-env-test",
+        "test": "pod-environment-variables",
+        "language": "rhai"
+    }, #{
+        "NODE_ENV": "test",
+        "DATABASE_URL": "postgres://localhost:5432/test",
+        "API_KEY": "test-api-key-12345",
+        "LOG_LEVEL": "debug",
+        "PORT": "80"
+    });
+    print("✓ Created pod with environment variables: " + result);
+} catch(e) {
+    print("❌ Failed to create pod with env vars: " + e);
+    throw e;
+}
+
+// Test 2: Create pod without environment variables
+print("\n--- Test 2: Create Pod without Environment Variables ---");
+
+try {
+    delete_pod(km, "rhai-pod-no-env-test");
+} catch(e) {
+    // Ignore cleanup errors
+}
+
+try {
+    let result = km.create_pod("rhai-pod-no-env-test", "nginx:latest", #{
+        "app": "rhai-pod-no-env-test",
+        "test": "no-environment-variables"
+    });
+    print("✓ Created pod without environment variables: " + result);
+} catch(e) {
+    print("❌ Failed to create pod without env vars: " + e);
+    throw e;
+}
+
+// Test 3: Create pod with special characters in env vars
+print("\n--- Test 3: Create Pod with Special Characters in Env Vars ---");
+
+try {
+    delete_pod(km, "rhai-pod-special-env-test");
+} catch(e) {
+    // Ignore cleanup errors
+}
+
+try {
+    let result = km.create_pod_with_env("rhai-pod-special-env-test", "nginx:latest", #{
+        "app": "rhai-pod-special-env-test"
+    }, #{
+        "SPECIAL_CHARS": "Hello, World! @#$%^&*()",
+        "JSON_CONFIG": "{\"key\": \"value\", \"number\": 123}",
+        "URL_WITH_PARAMS": "https://api.example.com/v1/data?param1=value1&param2=value2"
+    });
+    print("✓ Created pod with special characters in env vars: " + result);
+} catch(e) {
+    print("❌ Failed to create pod with special env vars: " + e);
+    throw e;
+}
+
+// Test 4: Verify resource listing
+print("\n--- Test 4: Verify Pod Listing ---");
+try {
+    let pods = pods_list(km);
+    print("✓ Found " + pods.len() + " pods");
+    
+    let found_env_test = false;
+    let found_no_env_test = false;
+    let found_special_env_test = false;
+    
+    for pod in pods {
+        if pod.contains("rhai-pod-env-test") {
+            found_env_test = true;
+            print("✓ Found rhai-pod-env-test pod");
+        }
+        if pod.contains("rhai-pod-no-env-test") {
+            found_no_env_test = true;
+            print("✓ Found rhai-pod-no-env-test pod");
+        }
+        if pod.contains("rhai-pod-special-env-test") {
+            found_special_env_test = true;
+            print("✓ Found rhai-pod-special-env-test pod");
+        }
+    }
+    
+    if found_env_test && found_no_env_test && found_special_env_test {
+        print("✓ All expected pods found");
+    } else {
+        print("❌ Some expected pods not found");
+    }
+} catch(e) {
+    print("❌ Failed to list pods: " + e);
+}
+
+// Cleanup
+print("\n--- Cleanup ---");
+try {
+    delete_pod(km, "rhai-pod-env-test");
+    print("✓ Deleted pod: rhai-pod-env-test");
+} catch(e) {
+    print("⚠ Failed to delete rhai-pod-env-test: " + e);
+}
+
+try {
+    delete_pod(km, "rhai-pod-no-env-test");
+    print("✓ Deleted pod: rhai-pod-no-env-test");
+} catch(e) {
+    print("⚠ Failed to delete rhai-pod-no-env-test: " + e);
+}
+
+try {
+    delete_pod(km, "rhai-pod-special-env-test");
+    print("✓ Deleted pod: rhai-pod-special-env-test");
+} catch(e) {
+    print("⚠ Failed to delete rhai-pod-special-env-test: " + e);
+}
+
+print("\n=== Pod Environment Variables Rhai Test Complete ===");
+print("✅ All tests passed successfully!");