refactor: reorganize project structure with modern C++ namespace organization

- Restructure include/ and src/ directories with logical grouping
- Move core components to spore/core/ (NodeContext, NetworkManager, TaskManager, ClusterManager, ApiServer)
- Move services to spore/services/ (NodeService, NetworkService, ClusterService, TaskService)
- Move types to spore/types/ (NodeInfo, ApiTypes, Config)
- Move internal components to spore/internal/ (Globals)
- Update all #include statements to use new namespace paths
- Update platformio.ini build filters for all environments
- Update all example files to use new include paths
- Maintain backward compatibility for public API
- Improve code organization, maintainability, and scalability

This reorganization follows modern C++ project structure patterns and provides
clear separation between public API, internal implementation, and utilities.
All examples compile successfully with the new structure.

include/spore/internal/Globals.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+
+// Cluster protocol and API constants
+namespace ClusterProtocol {
+    constexpr const char* DISCOVERY_MSG = "CLUSTER_DISCOVERY";
+    constexpr const char* RESPONSE_MSG = "CLUSTER_RESPONSE";
+    constexpr uint16_t UDP_PORT = 4210;
+    constexpr size_t UDP_BUF_SIZE = 64;
+    constexpr const char* API_NODE_STATUS = "/api/node/status";
+}
+
+namespace TaskIntervals {
+    constexpr unsigned long SEND_DISCOVERY = 1000;
+    constexpr unsigned long LISTEN_FOR_DISCOVERY = 100;
+    constexpr unsigned long UPDATE_STATUS = 1000;
+    constexpr unsigned long PRINT_MEMBER_LIST = 5000;
+    constexpr unsigned long HEARTBEAT = 2000;
+    constexpr unsigned long UPDATE_ALL_MEMBERS_INFO = 10000;
+}
+
+constexpr unsigned long NODE_ACTIVE_THRESHOLD = 10000;
+constexpr unsigned long NODE_INACTIVE_THRESHOLD = 60000;
+constexpr unsigned long NODE_DEAD_THRESHOLD = 120000;
+