feat(mcp): restore MCP service with display charging toggle

- Restore MCP system (McpSystem 1900+ LOC, McpHandler, McpScreensaver, McpSettings, McpOverride apps)
- Use audio-stream instead of direct I2S for MP3 playback (fixes fast playback, uses native resampler)
- Register McpSettings + McpOverride in Tactility.cpp so Settings shows MCP Screen
- DisplaySettings: add ScreensaverType::McpScreen and disableScreensaverWhenCharging flag
- Display app: add 'Disable on charging' toggle, handles McpScreen screensaver type
- DisplayIdle: skip screensaver while charging, support McpScreen screensaver, isDeviceCharging check via PowerDevice
- WebServer: coexistence with MCP (McpHandler)
- Avoid formatting churn from previous commits

Squashed from range eaa248b0..8970143f (6 commits) into single clean commit

Tactility/Source/service/webserver/WebServerService.cpp

@@ -5,6 +5,8 @@
 #include <Tactility/service/webserver/AssetVersion.h>
 #include <Tactility/service/ServiceManifest.h>
 #include <Tactility/settings/WebServerSettings.h>
+#include <Tactility/settings/McpSettings.h>
+#include <Tactility/mcp/McpSystem.h>
 #include <Tactility/MountPoints.h>
 #include <Tactility/file/File.h>
 #include <Tactility/lvgl/Statusbar.h>
@@ -215,7 +217,8 @@ bool WebServerService::onStart(ServiceContext& service) {
         lock.lock();
         g_cachedSettings = settings::webserver::loadOrGetDefault();
         g_settingsCached = true;
-        serverEnabled = g_cachedSettings.webServerEnabled;
+        auto mcpSettings = settings::mcp::loadOrGetDefault();
+        serverEnabled = g_cachedSettings.webServerEnabled || mcpSettings.mcpEnabled;
     }
     // Subscribe to settings change events to refresh cache
     settingsEventSubscription = pubsub->subscribe([](WebServerEvent event) {
@@ -259,13 +262,17 @@ void WebServerService::onStop(ServiceContext& service) {
 void WebServerService::setEnabled(bool enabled) {
     auto lock = mutex.asScopedLock();
     lock.lock();
-    
+
     if (enabled) {
         if (!httpServer || !httpServer->isStarted()) {
             startServer();
         }
     } else {
-        if (httpServer && httpServer->isStarted()) {
+        // Stop only if both web server and MCP are disabled
+        auto wsSettings = settings::webserver::loadOrGetDefault();
+        auto mcpSettings = settings::mcp::loadOrGetDefault();
+        bool anyEnabled = wsSettings.webServerEnabled || mcpSettings.mcpEnabled;
+        if (!anyEnabled && httpServer && httpServer->isStarted()) {
             stopServer();
         }
     }
@@ -514,6 +521,11 @@ bool WebServerService::startServer() {
     LOG_I(TAG, "HTTP server started successfully on port %u", (unsigned)settings.webServerPort);
     publish_event(this, WebServerEvent::WebServerStarted);
 
+    auto mcpSettings = settings::mcp::loadOrGetDefault();
+    if (mcpSettings.mcpEnabled) {
+        mcp::startVideoStreamServer();
+    }
+
     // Show statusbar icon
     if (statusbarIconId >= 0) {
         lvgl::statusbar_icon_set_image(statusbarIconId, LVGL_ICON_STATUSBAR_CLOUD);
@@ -533,6 +545,8 @@ void WebServerService::stopServer() {
     httpServer->stop();
     httpServer.reset();
 
+    mcp::stopVideoStreamServer();
+
     // Stop AP mode WiFi if we started it
     if (apWifiInitialized || apNetif != nullptr) {
         stopApMode();
@@ -1025,15 +1039,24 @@ esp_err_t WebServerService::handleApiGet(httpd_req_t* request) {
     return ESP_FAIL;
 }
 
-// API POST dispatcher - all POST endpoints require authentication
+// API POST dispatcher - all POST endpoints require authentication except MCP
 esp_err_t WebServerService::handleApiPost(httpd_req_t* request) {
+    const char* uri = request->uri;
+
+    // MCP endpoints are unauthenticated (local network)
+    if (strncmp(uri, "/api/mcp", 8) == 0) {
+        return handleApiMcp(request);
+    }
+    if (strncmp(uri, "/api/screen/raw", 15) == 0) {
+        return handleApiScreenRaw(request);
+    }
+
     bool authPassed = false;
     esp_err_t authResult = validateRequestAuth(request, authPassed);
     if (!authPassed) {
         return authResult;
     }
 
-    const char* uri = request->uri;
     if (strncmp(uri, "/api/apps/run", 13) == 0) {
         return handleApiAppsRun(request);
     }