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/service/displayidle/DisplayIdle.cpp

@@ -12,6 +12,7 @@
 #include <Tactility/Logger.h>
 #include <Tactility/CoreDefines.h>
 #include <Tactility/hal/display/DisplayDevice.h>
+#include <Tactility/hal/power/PowerDevice.h>
 #include <Tactility/lvgl/LvglSync.h>
 #include <Tactility/service/ServiceContext.h>
 #include <Tactility/service/ServiceManifest.h>
@@ -30,6 +31,22 @@ static std::shared_ptr<hal::display::DisplayDevice> getDisplay() {
     return hal::findFirstDevice<hal::display::DisplayDevice>(hal::Device::Type::Display);
 }
 
+static bool isDeviceCharging() {
+    bool charging = false;
+    hal::findDevices<hal::power::PowerDevice>(hal::Device::Type::Power, [&charging](const auto& power) {
+        if (!power->supportsMetric(hal::power::PowerDevice::MetricType::IsCharging)) {
+            return true; // continue
+        }
+        hal::power::PowerDevice::MetricData data;
+        if (power->getMetric(hal::power::PowerDevice::MetricType::IsCharging, data) && data.valueAsBool) {
+            charging = true;
+            return false; // stop iter
+        }
+        return true;
+    });
+    return charging;
+}
+
 void DisplayIdleService::stopScreensaverCb(lv_event_t* e) {
     auto* self = static_cast<DisplayIdleService*>(lv_event_get_user_data(e));
     self->stopScreensaverLocked();
@@ -178,43 +195,53 @@ void DisplayIdleService::tick() {
     }
 
     auto display = getDisplay();
-    if (display != nullptr && display->supportsBacklightDuty()) {
+    bool supportsBacklight = display != nullptr && display->supportsBacklightDuty();
+
+    if (supportsBacklight) {
         if (!cachedDisplaySettings.backlightTimeoutEnabled || cachedDisplaySettings.backlightTimeoutMs == 0) {
             if (displayDimmed) {
                 display->setBacklightDuty(cachedDisplaySettings.backlightDuty);
                 displayDimmed = false;
             }
         } else {
+            bool charging_blocks = cachedDisplaySettings.disableScreensaverWhenCharging && isDeviceCharging();
+
             if (!displayDimmed && inactive_ms >= cachedDisplaySettings.backlightTimeoutMs) {
-                if (!lvgl::lock(100)) {
-                    return; // Retry on next tick
+                if (charging_blocks) {
+                    // Skip screensaver while charging
+                } else {
+                    if (!lvgl::lock(100)) {
+                        return; // Retry on next tick
+                    }
+                    activateScreensaver();
+                    lvgl::unlock();
+                    if (cachedDisplaySettings.screensaverType == settings::display::ScreensaverType::None) {
+                        display->setBacklightDuty(0);
+                    }
+                    displayDimmed = true;
                 }
-                activateScreensaver();
-                lvgl::unlock();
-                // Turn off backlight for "None" screensaver (just black screen)
-                if (cachedDisplaySettings.screensaverType == settings::display::ScreensaverType::None) {
-                    display->setBacklightDuty(0);
+            } else if (displayDimmed) {
+                if (inactive_ms < kWakeActivityThresholdMs) {
+                    stopScreensaver();
+                } else if (charging_blocks) {
+                    stopScreensaver();
                 }
-                displayDimmed = true;
-            } else if (displayDimmed && (inactive_ms < kWakeActivityThresholdMs)) {
-                stopScreensaver();
             }
         }
     }
 }
 
 bool DisplayIdleService::onStart(ServiceContext& service) {
-    auto display = getDisplay();
-    if (display != nullptr && !display->supportsBacklightDuty()) {
-        LOGGER.info("Monochrome/RLCD display detected (no backlight control): disabling screensaver tick timer");
-        return true;
-    }
-
     // Seed random number generator for varied screensaver patterns
     srand(static_cast<unsigned int>(time(nullptr)));
 
     cachedDisplaySettings = settings::display::loadOrGetDefault();
 
+    auto display = getDisplay();
+    if (display != nullptr && !display->supportsBacklightDuty()) {
+        LOGGER.info("Monochrome/RLCD display detected (no backlight control): idle timer will run but auto-backlight off is disabled");
+    }
+
     timer = std::make_unique<Timer>(Timer::Type::Periodic, kernel::millisToTicks(TICK_INTERVAL_MS), [this]{ this->tick(); });
     timer->setCallbackPriority(Thread::Priority::Lower);
     timer->start();
@@ -297,10 +324,12 @@ void DisplayIdleService::startMcpScreensaver() {
     screensaverActiveCounter = 0;
     backlightOff = false;
 
-    // Ensure backlight is active and set to configured duty cycle
+    // Ensure backlight is active if the display supports it
     auto display = getDisplay();
-    if (display) {
-        display->setBacklightDuty(cachedDisplaySettings.backlightDuty);
+    if (display != nullptr && display->supportsBacklightDuty()) {
+        uint8_t duty = cachedDisplaySettings.backlightDuty;
+        if (duty == 0) duty = 255; // ensure visible if settings not loaded / default
+        display->setBacklightDuty(duty);
     }
 
     lv_coord_t screenW = lv_display_get_horizontal_resolution(nullptr);