feat: X3 clock display with DS3231 RTC and NTP sync (#1612)

src/activities/settings/ClockSyncActivity.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "activities/Activity.h"
+
+// Manual NTP resync action. Runs a forced sync (bypassing the once-per-device debounce),
+// reports success/failure, then waits for Back. Requires WiFi to already be connected.
+class ClockSyncActivity final : public Activity {
+ public:
+  explicit ClockSyncActivity(GfxRenderer& renderer, MappedInputManager& mappedInput)
+      : Activity("ClockSync", renderer, mappedInput) {}
+
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+  bool skipLoopDelay() override { return true; }
+  void render(RenderLock&&) override;
+
+ private:
+  enum State { SYNCING, SUCCESS, NO_WIFI, FAILED };
+  State state = SYNCING;
+  char syncedTime[16] = {0};
+
+  void runSync();
+};