Fix Task WDT crashes: LVGL priority starvation + BLE WDT false positives

Two root causes for frequent device reboots:

1. LVGL task (priority 2) starved loopTask (priority 1) on core 1.
   During heavy screen rendering, loopTask couldn't run for 30+ seconds,
   triggering the Task WDT. Fixed by lowering LVGL to priority 1 so
   FreeRTOS round-robins both tasks fairly.

2. BLE task was registered with the 30s Task WDT, but blocking NimBLE
   GATT operations (connect + service discovery + subscribe + read) can
   legitimately take 30-60s total. Removed BLE task from WDT since
   NimBLE has its own internal ~30s timeouts per GATT operation.

Also added ble_hs_synced() guards to write(), read(), notify(),
writeCharacteristic(), discoverServices(), and enableNotifications()
to prevent use-after-free on stale NimBLE client pointers during
host resets.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/ble_interface/BLEInterface.cpp

@@ -10,7 +10,6 @@
 #ifdef ARDUINO
 #include <Arduino.h>
 #include <esp_heap_caps.h>
-#include <esp_task_wdt.h>
 #endif
 
 using namespace RNS;
@@ -1136,12 +1135,13 @@ void BLEInterface::ble_task(void* param) {
     BLEInterface* self = static_cast<BLEInterface*>(param);
     Serial.printf("BLE task started on core %d\n", xPortGetCoreID());
 
-    // Subscribe BLE task to Task Watchdog — detects BLE deadlocks
-    esp_task_wdt_add(NULL);
+    // NOTE: BLE task is intentionally NOT subscribed to the FreeRTOS Task WDT.
+    // Blocking NimBLE GATT operations (service discovery, subscribe, read, write)
+    // each have ~30s internal timeouts. A full connect chain (connect + discover +
+    // enable notifications + identity read) can legitimately block 30-60s total,
+    // which exceeds the 30s WDT. NimBLE's own timeouts provide recovery.
 
     while (true) {
-        esp_task_wdt_reset();
-
         // Run the BLE loop (already has internal mutex protection)
         self->loop();