v1.7.1: GPS time sync, timezone picker, status bar clock

- GPS time sync via UBlox MIA-M10Q (38400 baud auto-detect)
- Custom zero-dependency NMEA parser with XOR checksum validation
- Only trust GPS time when satellites > 0 (no stale RTC cache)
- DST-aware timezone picker at first boot (21 cities, POSIX TZ strings)
- Timezone also configurable in Settings > GPS/Time
- GPS Time on by default, GPS Location off by default (opt-in)
- Status bar: clock (top-left), Ratspeak.org (center), battery (right)
- 12h time default (no AM/PM), configurable 24h in settings
- NVS persistence of GPS time for approximate timestamps across reboots
- Fix factory reset Enter key bleed-through (600ms input guard)
- Fix hardcoded UTC-5 NTP timezone (now uses DST-aware POSIX TZ)

src/ui/LvStatusBar.cpp

@@ -32,13 +32,6 @@ void LvStatusBar::create(lv_obj_t* parent) {
     lv_label_set_text(_lblBrand, "Ratspeak.org");
     lv_obj_align(_lblBrand, LV_ALIGN_CENTER, 0, 0);
 
-    // Right: GPS indicator (left of battery, hidden until fix)
-    _lblGPS = lv_label_create(_bar);
-    lv_obj_set_style_text_font(_lblGPS, font, 0);
-    lv_obj_set_style_text_color(_lblGPS, lv_color_hex(Theme::PRIMARY), 0);
-    lv_label_set_text(_lblGPS, "");
-    lv_obj_align(_lblGPS, LV_ALIGN_RIGHT_MID, -42, 0);
-
     // Right: Battery %
     _lblBatt = lv_label_create(_bar);
     lv_obj_set_style_text_font(_lblBatt, font, 0);
@@ -104,11 +97,7 @@ void LvStatusBar::updateTime() {
 }
 
 void LvStatusBar::setGPSFix(bool hasFix) {
-    if (_gpsFix == hasFix) return;
     _gpsFix = hasFix;
-    if (_lblGPS) {
-        lv_label_set_text(_lblGPS, hasFix ? "GPS" : "");
-    }
 }
 
 void LvStatusBar::setBatteryPercent(int pct) {