feat(gat562-30s): add solo build envs, fix joystick/GPS/buzzer/display

- SSD1306Display: track _text_sz in setTextSize(); override getCharWidth()
  and getLineHeight() so line spacing scales with text size (fixes text
  overlap on splash/clock screens at size 2)
- gat562_30s_mesh_kit variant.h: fix PIN_GPS_EN 33→34 (IO2/P1.02 controls
  GPS module power via Q3/Q5 transistors; 33 = BEE_EN = buzzer)
- gat562_30s_mesh_kit variant.h: correct joystick pin comments (P0.xx labels
  were cyclically wrong; pin numbers already correct)
- gat562_30s_mesh_kit target.h/cpp: declare and instantiate joystick_up/down
  under UI_HAS_JOYSTICK_UPDOWN guard (fixes compile error in solo envs)
- gat562_30s_mesh_kit platformio.ini: add solo_ble and solo_dual environments
  with GPS, BLE, joystick up/down, QSPI flash, and buzzer (NonBlockingRTTTL)
- gat562_mesh_watch13 platformio.ini: add solo_ble environment with GPS

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

src/helpers/ui/SSD1306Display.h

@@ -19,6 +19,7 @@ class SSD1306Display : public DisplayDriver {
   Adafruit_SSD1306 display;
   bool _isOn;
   uint8_t _color;
+  int _text_sz = 1;
   RefCountedDigitalPin* _peripher_power;
 
   bool i2c_probe(TwoWire& wire, uint8_t addr);
@@ -31,6 +32,9 @@ public:
   }
   bool begin();
 
+  int getCharWidth()  const override { return 6 * _text_sz; }
+  int getLineHeight() const override { return 8 * _text_sz; }
+
   bool isOn() override { return _isOn; }
   void turnOn() override;
   void turnOff() override;