Fix clippy warnings and align Makefile with CI

- Remove redundant single-component path imports of tracing_subscriber
  from all example files
- Update Makefile lint target to use --all-targets --all-features
  to match CI configuration and justfile

This ensures make lint catches the same issues as CI clippy checks.

Author: peteski22

Makefile

@@ -47,7 +47,7 @@ examples:
 
 .PHONY: lint
 lint:
-	cargo clippy -- -D warnings
+	cargo clippy --all-targets --all-features -- -D warnings
 
 .PHONY: fmt
 fmt:

examples/auth_plugin/main.rs

@@ -10,7 +10,6 @@ use std::collections::HashSet;
 use std::sync::Arc;
 use tokio::sync::RwLock;
 use tonic::{Request, Response, Status};
-use tracing_subscriber;
 
 struct AuthPlugin {
     valid_tokens: Arc<RwLock<HashSet<String>>>,

examples/rate_limit_plugin/main.rs

@@ -11,7 +11,6 @@ use std::sync::Arc;
 use std::time::{Duration, Instant};
 use tokio::sync::Mutex;
 use tonic::{Request, Response, Status};
-use tracing_subscriber;
 
 #[derive(Debug, Clone)]
 struct TokenBucket {

examples/simple_plugin/main.rs

@@ -7,7 +7,6 @@ use mcpd_plugins_sdk::{
     serve, Capabilities, HttpRequest, HttpResponse, Metadata, Plugin, FLOW_REQUEST,
 };
 use tonic::{Request, Response, Status};
-use tracing_subscriber;
 
 struct SimplePlugin;