Add WiFi reconnection retry logic to recover from unreliable WiFi

- Implement periodic WiFi reconnection attempts when stuck in AP mode
- Add WIFI_RECONNECT_INTERVAL_MS config (default 60s) for configurable retry frequency
- Prevent data loss by automatically attempting to switch back to STA mode
- Maintain AP mode for manual configuration if reconnection fails
- Track WiFi config and last reconnection attempt time in shared state
- Add wifi_try_reconnect_sta() and wifi_restore_ap_mode() helper functions
- Log reconnection attempts and results for debugging

src/app_context.h

@@ -4,6 +4,7 @@
 
 #include "config.h"
 #include "data_model.h"
+#include "wifi_manager.h"
 
 struct ReceiverSharedState {
   SenderStatus sender_statuses[NUM_SENDERS];
@@ -24,5 +25,11 @@ struct ReceiverSharedState {
   uint32_t receiver_last_error_ms;
   bool receiver_discovery_sent;
   bool ap_mode;
+  
+  // WiFi configuration and reconnection tracking
+  WifiMqttConfig wifi_config;
+  uint32_t last_wifi_reconnect_attempt_ms;
+  char ap_ssid[32];  // AP SSID for restoring AP mode if reconnection fails
+  char ap_password[32];  // AP password for restoring AP mode
 };