fix(uwb_tag): turn display ON after initialization and add button wake

- Display was never turned on after display.begin() in setup()
- Added SSD1306_DISPLAYON command after initialization
- Added short button press detection to wake display
- Fixes blank display issue reported by SAUL

esp32/uwb_tag/src/main.cpp

@@ -766,7 +766,7 @@ static void pm_update(void) {
             pm_enter_deep_sleep();
         }
     } else {
-        g_btn_held_ms = 0;
+        if (g_btn_held_ms > 0 && (now - g_btn_held_ms) < 1000) { g_pm_last_activity_ms = now; display.ssd1306_command(SSD1306_DISPLAYON); } g_btn_held_ms = 0;
     }
 }
 
@@ -969,6 +969,9 @@ void setup(void) {
         Serial.println("[uwb_tag] WARN: SSD1306 not found");
     } else {
         display.clearDisplay();
+        display.ssd1306_command(SSD1306_DISPLAYON);  // Turn display ON!
+        display.ssd1306_command(SSD1306_SETCONTRAST);
+        display.ssd1306_command(g_cfg.display_brightness);
         display.setTextSize(2);
         display.setTextColor(SSD1306_WHITE);
         display.setCursor(0, 0);