fix: skip NTP sync and mDNS in deep sleep wake path to reduce battery drain

The syncNTP() call blocks up to 5 seconds waiting for NTP response on
every deep sleep wake cycle (every 10 minutes). Combined with mDNS
startup, this added significant active WiFi time per cycle.

Fix: Add 'minimal' flag to WiFiManager::begin()/startStation(). In
the deep sleep wake path, skip NTP sync and mDNS entirely. The system
clock is already seeded from the hardware RTC at boot, which is
accurate enough for 30-day date window calculations.

Normal interactive boot still does full NTP sync + mDNS as before.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/main.cpp

@@ -429,8 +429,8 @@ void timerWakeCycle() {
 
     Settings s = settingsManager.get();
 
-    // Connect WiFi (blocking)
-    wifiManager.begin(settingsManager);
+    // Connect WiFi (minimal — skip NTP/mDNS to save battery)
+    wifiManager.begin(settingsManager, true);
     if (!wifiManager.isConnected()) {
         Serial.println("[timer_wake] WiFi failed — going back to sleep");
         powerManager.enterDeepSleep(s.interval_min);