fix: MCP settings persistence + WebServer/DevServer coexistence + screensaver charging toggle

- McpSettings was hardcoded to /data/service/mcp/settings.properties,
  but ES3C28P uses storage.userDataLocation=SD so user data lives on
  /sdcard/tactility/. Settings appeared to save but on reload returned
  default false -> "enable and when I go back shows disabled".
  Fixed to use getUserDataPath()+"/settings/mcp.properties" pattern
  consistent with DisplaySettings/WebServerSettings, with
  findOrCreateParentDirectory() and isFile() guard.

- HttpServer ctrl_port collision: ESP-IDF default 32768 used by both
  WebServer (80) and DevelopmentService (6666). Second httpd_start()
  failed silently -> dashboard up but /api/mcp 404 and :6666 refused.
  Fixed with unique ctrl_port = 32768 + (port % 1000).
  Added CONFIG_HTTPD_MAX_URI_HANDLERS=20 (default 8 < 9 needed for
  7 handlers + 2 internal).

- DevService stack 5120 -> 8192 for /app/install handling.
- McpSystem video stream task stack 4096 -> 8192 and idle yield 50ms
  (was 5ms always) to avoid CPU starvation blocking httpd tasks.
  On RLCD, timer must always run: DisplayIdle early return on
  !supportsBacklightDuty() broke MCP manual activation (cachedSettings
  not loaded, backlight duty 0). Fixed to always load settings +
  start timer, log RLCD detection, guard setBacklightDuty with
  supportsBacklightDuty() and fallback duty 255.

- DisplaySettings: add disableScreensaverWhenCharging bool, persisted,
  with UI toggle in Display app (Settings->Display) using
  PowerDevice::IsCharging check via findDevices callback.
  When charging and flag enabled, screensaver activation skipped,
  and if already dimmed, wake on charging.

- ES3C28P Power driver: GPIO9 ADC1_CH8 2x divider 2500-4200mV spec from
  ~/Downloads official docs, TP4054 CHRG not connected to GPIO, so
  IsCharging inferred via voltage thresholds (<500mV no battery USB
  or >5000mV wall powered, >=4150mV high) + rising trend.

Verified: flashed es3c28p to /dev/cu.usbmodem101 (192.168.68.113),
WiFi FamReynaMesh RSSI -59, dashboard 200, :6666/info now works,
/api/mcp returns disabled correctly until enabled, persists to SD.

Tactility/Source/app/display/Display.cpp

@@ -41,6 +41,8 @@ class DisplayApp final : public App {
     lv_obj_t* timeoutSwitch = nullptr;
     lv_obj_t* timeoutDropdown = nullptr;
     lv_obj_t* screensaverDropdown = nullptr;
+    lv_obj_t* disableWhenChargingWrapper = nullptr;
+    lv_obj_t* disableWhenChargingSwitch = nullptr;
 
     static void onBacklightSliderEvent(lv_event_t* event) {
         auto* slider = static_cast<lv_obj_t*>(lv_event_get_target(event));
@@ -95,15 +97,29 @@ class DisplayApp final : public App {
                 if (app->screensaverDropdown) {
                     lv_obj_clear_state(app->screensaverDropdown, LV_STATE_DISABLED);
                 }
+                if (app->disableWhenChargingWrapper) {
+                    lv_obj_clear_state(app->disableWhenChargingWrapper, LV_STATE_DISABLED);
+                }
             } else {
                 lv_obj_add_state(app->timeoutDropdown, LV_STATE_DISABLED);
                 if (app->screensaverDropdown) {
                     lv_obj_add_state(app->screensaverDropdown, LV_STATE_DISABLED);
                 }
+                if (app->disableWhenChargingWrapper) {
+                    lv_obj_add_state(app->disableWhenChargingWrapper, LV_STATE_DISABLED);
+                }
             }
         }
     }
 
+    static void onDisableWhenChargingChanged(lv_event_t* event) {
+        auto* app = static_cast<DisplayApp*>(lv_event_get_user_data(event));
+        auto* sw = static_cast<lv_obj_t*>(lv_event_get_target(event));
+        bool enabled = lv_obj_has_state(sw, LV_STATE_CHECKED);
+        app->displaySettings.disableScreensaverWhenCharging = enabled;
+        app->displaySettingsUpdated = true;
+    }
+
     static void onTimeoutChanged(lv_event_t* event) {
         auto* app = static_cast<DisplayApp*>(lv_event_get_user_data(event));
         auto* dropdown = static_cast<lv_obj_t*>(lv_event_get_target(event));
@@ -294,6 +310,26 @@ public:
             if (!displaySettings.backlightTimeoutEnabled) {
                 lv_obj_add_state(screensaverDropdown, LV_STATE_DISABLED);
             }
+
+            // Disable screensaver when charging toggle
+            disableWhenChargingWrapper = lv_obj_create(main_wrapper);
+            lv_obj_set_size(disableWhenChargingWrapper, LV_PCT(100), LV_SIZE_CONTENT);
+            lv_obj_set_style_pad_all(disableWhenChargingWrapper, 0, LV_STATE_DEFAULT);
+            lv_obj_set_style_border_width(disableWhenChargingWrapper, 0, LV_STATE_DEFAULT);
+
+            auto* charging_label = lv_label_create(disableWhenChargingWrapper);
+            lv_label_set_text(charging_label, "Disable on charging");
+            lv_obj_align(charging_label, LV_ALIGN_LEFT_MID, 0, 0);
+
+            disableWhenChargingSwitch = lv_switch_create(disableWhenChargingWrapper);
+            if (displaySettings.disableScreensaverWhenCharging) {
+                lv_obj_add_state(disableWhenChargingSwitch, LV_STATE_CHECKED);
+            }
+            lv_obj_align(disableWhenChargingSwitch, LV_ALIGN_RIGHT_MID, 0, 0);
+            lv_obj_add_event_cb(disableWhenChargingSwitch, onDisableWhenChargingChanged, LV_EVENT_VALUE_CHANGED, this);
+            if (!displaySettings.backlightTimeoutEnabled) {
+                lv_obj_add_state(disableWhenChargingWrapper, LV_STATE_DISABLED);
+            }
         }
 
         if (hasCalibratableTouchDevice()) {