v1.2.0: Firmware refactor to service-oriented architecture + WiFi fixes

Firmware:
- Fixed WiFi reconnection bug after power cycle by adding WiFi.persistent(false)
  and disabling auto-connect/auto-reconnect
- Fixed AP mode not broadcasting by properly handling WIFI_AP_STA mode transitions
- Refactored to service-oriented architecture:
  - device_state: Central state management with event callbacks
  - config_service: NVS persistence (renamed from config_manager)
  - wifi_service: WiFi STA/AP management (extracted from main.cpp)
  - mqtt_service: MQTT client and message routing (extracted from main.cpp)
  - ble_service: BLE GATT services (renamed from ble_services)
  - web_service: HTTP configuration portal (renamed from web_portal)
- main.cpp reduced from ~470 lines to ~60 lines (thin orchestrator)
- Each service is self-contained with setup()/loop() pattern

Backend:
- Added heart rate variation endpoint
- UI improvements

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

firmware/esp32_ble_sim/include/services/ble_service.h

@@ -0,0 +1,58 @@
+#ifndef BLE_SERVICE_H
+#define BLE_SERVICE_H
+
+#include <Arduino.h>
+
+// ============================================
+// BLE Service UUIDs (Bluetooth SIG standard)
+// ============================================
+#define HEART_RATE_SERVICE_UUID        "180D"
+#define HEART_RATE_MEASUREMENT_UUID    "2A37"
+#define BODY_SENSOR_LOCATION_UUID      "2A38"
+#define BATTERY_SERVICE_UUID           "180F"
+#define BATTERY_LEVEL_UUID             "2A19"
+#define FITNESS_MACHINE_SERVICE_UUID   "1826"
+#define TREADMILL_DATA_UUID            "2ACD"
+#define FITNESS_MACHINE_FEATURE_UUID   "2ACC"
+
+// ============================================
+// BLE Service
+// Manages BLE advertising and GATT services
+// ============================================
+class BleService {
+public:
+    static BleService& getInstance();
+
+    // Prevent copying
+    BleService(const BleService&) = delete;
+    BleService& operator=(const BleService&) = delete;
+
+    // Lifecycle
+    void setup();
+    void loop();
+
+    // Configuration
+    void setupHeartRate();
+    void setupTreadmill();
+    void stop();
+
+    // Notifications
+    void notifyHeartRate(uint8_t bpm);
+    void notifyTreadmill(uint16_t speed, int16_t incline, uint32_t distance);
+    void updateBattery(uint8_t level);
+
+    // State
+    bool isClientConnected() const { return deviceConnected; }
+
+private:
+    BleService() = default;
+
+    bool deviceConnected = false;
+    unsigned long lastNotify = 0;
+
+    void initBLE();
+};
+
+#define bleService BleService::getInstance()
+
+#endif // BLE_SERVICE_H

firmware/esp32_ble_sim/include/services/config_service.h

@@ -0,0 +1,64 @@
+#ifndef CONFIG_SERVICE_H
+#define CONFIG_SERVICE_H
+
+#include <Arduino.h>
+#include <Preferences.h>
+
+// ============================================
+// Config Service
+// Manages persistent configuration in NVS
+// ============================================
+class ConfigService {
+public:
+    static ConfigService& getInstance();
+
+    // Prevent copying
+    ConfigService(const ConfigService&) = delete;
+    ConfigService& operator=(const ConfigService&) = delete;
+
+    // Load config from NVS
+    bool load();
+
+    // Save config to NVS
+    void save();
+
+    // Clear all config
+    void clear();
+
+    // Check if configured
+    bool isConfigured() const { return configured; }
+
+    // Getters
+    const String& getWifiSsid() const { return wifiSsid; }
+    const String& getWifiPassword() const { return wifiPassword; }
+    const String& getMqttHost() const { return mqttHost; }
+    uint16_t getMqttPort() const { return mqttPort; }
+    const String& getDeviceId() const { return deviceId; }
+
+    // Setters
+    void setWifiCredentials(const String& ssid, const String& password);
+    void setMqttConfig(const String& host, uint16_t port);
+    void setDeviceId(const String& id);
+
+    // Get unique AP name based on chip ID
+    String getAPName() const;
+
+    // Get unique default device ID based on chip ID
+    String getDefaultDeviceId() const;
+
+private:
+    ConfigService() = default;
+
+    bool configured = false;
+    String wifiSsid = "";
+    String wifiPassword = "";
+    String mqttHost = "";
+    uint16_t mqttPort = 1883;
+    String deviceId = "";
+
+    Preferences preferences;
+};
+
+#define configService ConfigService::getInstance()
+
+#endif // CONFIG_SERVICE_H

firmware/esp32_ble_sim/include/services/mqtt_service.h

@@ -0,0 +1,45 @@
+#ifndef MQTT_SERVICE_H
+#define MQTT_SERVICE_H
+
+#include <Arduino.h>
+
+// ============================================
+// MQTT Service
+// Manages MQTT connection and message routing
+// ============================================
+class MqttService {
+public:
+    static MqttService& getInstance();
+
+    // Prevent copying
+    MqttService(const MqttService&) = delete;
+    MqttService& operator=(const MqttService&) = delete;
+
+    // Lifecycle
+    void setup();
+    void loop();
+
+    // State
+    bool isConnected() const { return mqttConnected; }
+
+    // Publishing
+    void publishStatus();
+    void publishValues();
+
+private:
+    MqttService() = default;
+
+    bool mqttConnected = false;
+    unsigned long lastMqttAttempt = 0;
+    unsigned long lastStatusReport = 0;
+
+    void connectToMQTT();
+    void handleMessage(char* topic, byte* payload, unsigned int length);
+
+    // Static callback wrapper for PubSubClient
+    static void messageCallback(char* topic, byte* payload, unsigned int length);
+};
+
+#define mqttService MqttService::getInstance()
+
+#endif // MQTT_SERVICE_H

firmware/esp32_ble_sim/include/services/web_service.h

@@ -0,0 +1,35 @@
+#ifndef WEB_SERVICE_H
+#define WEB_SERVICE_H
+
+#include <Arduino.h>
+
+// ============================================
+// Web Service
+// Manages HTTP server for configuration portal
+// ============================================
+class WebService {
+public:
+    static WebService& getInstance();
+
+    // Prevent copying
+    WebService(const WebService&) = delete;
+    WebService& operator=(const WebService&) = delete;
+
+    // Lifecycle
+    void setup();
+    void loop();
+
+private:
+    WebService() = default;
+
+    void handleRoot();
+    void handleGetStatus();
+    void handlePostConfig();
+    void handleReset();
+    void handleResetDistance();
+    void handleSetBattery();
+};
+
+#define webService WebService::getInstance()
+
+#endif // WEB_SERVICE_H

firmware/esp32_ble_sim/include/services/wifi_service.h

@@ -0,0 +1,49 @@
+#ifndef WIFI_SERVICE_H
+#define WIFI_SERVICE_H
+
+#include <Arduino.h>
+
+// ============================================
+// WiFi Service
+// Manages WiFi STA and AP modes
+// ============================================
+class WiFiService {
+public:
+    static WiFiService& getInstance();
+
+    // Prevent copying
+    WiFiService(const WiFiService&) = delete;
+    WiFiService& operator=(const WiFiService&) = delete;
+
+    // Lifecycle
+    void setup();
+    void loop();
+
+    // State queries
+    bool isConnected() const { return wifiConnected; }
+    bool isApActive() const { return apModeActive; }
+    String getIP() const;
+
+    // Actions
+    void startAP();
+    void stopAP();
+    void reconnect();  // Trigger reconnection attempt
+
+private:
+    WiFiService() = default;
+
+    bool wifiConnected = false;
+    bool apModeActive = false;
+    unsigned long lastWifiAttempt = 0;
+    int wifiRetryCount = 0;
+
+    static const int MAX_WIFI_RETRIES = 5;
+
+    void connectToWiFi();
+    void startAPMode();
+    void stopAPMode();
+};
+
+#define wifiService WiFiService::getInstance()
+
+#endif // WIFI_SERVICE_H