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.

Cargo.toml

@@ -88,7 +88,8 @@ urlencoding = "2.1.3"
 tokio-test = "0.4.4"
 
 [dependencies]
-thiserror = "2.0.12" # For error handling in the main Error enum
+thiserror = "2.0.12"         # For error handling in the main Error enum
+tokio = { workspace = true } # For async examples
 
 # Optional dependencies - users can choose which modules to include
 sal-git = { path = "git", optional = true }
@@ -146,3 +147,19 @@ all = [
     "rhai",
     "service_manager",
 ]
+
+# Examples
+[[example]]
+name = "postgres_cluster"
+path = "examples/kubernetes/clusters/postgres.rs"
+required-features = ["kubernetes"]
+
+[[example]]
+name = "redis_cluster"
+path = "examples/kubernetes/clusters/redis.rs"
+required-features = ["kubernetes"]
+
+[[example]]
+name = "generic_cluster"
+path = "examples/kubernetes/clusters/generic.rs"
+required-features = ["kubernetes"]