feat: integrate MCP server and screen override into system firmware

- Add McpSettings (load/save mcpEnabled, mcpOverrideEnabled to /data/service/mcp/settings.properties)
- Add McpSystem: global state, canvas drawing (RGB565, BMP, PBM, text), I2S audio (WAV, MP3 via minimp3, tone, record)
- Add McpHandler: unauthenticated POST /api/mcp (JSON-RPC 2.0, 13 tools) and POST /api/screen/raw endpoints
- Route MCP endpoints before Basic Auth check in WebServerService::handleApiPost
- Start HTTP server at boot if either webServerEnabled OR mcpEnabled is set
- Fix setEnabled: start unconditionally when called with true; only stop if both WS and MCP are disabled
- Add McpSettingsApp (Settings category): toggle MCP service + screen override, show live endpoint URL
- Add McpOverrideApp (appId one.tactility.mcpscreen): full-screen LVGL canvas for LLM-driven display override
- Register both new apps in Tactility.cpp

Tactility/Source/service/webserver/WebServerService.cpp

@@ -5,6 +5,7 @@
 #include <Tactility/service/webserver/AssetVersion.h>
 #include <Tactility/service/ServiceManifest.h>
 #include <Tactility/settings/WebServerSettings.h>
+#include <Tactility/settings/McpSettings.h>
 #include <Tactility/MountPoints.h>
 #include <Tactility/file/File.h>
 #include <Tactility/Logger.h>
@@ -222,7 +223,9 @@ 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) {
@@ -236,10 +239,10 @@ bool WebServerService::onStart(ServiceContext& service) {
 
     // Start HTTP server only if enabled in settings (default: OFF to save memory)
     if (serverEnabled) {
-        LOGGER.info("WebServer enabled in settings, starting HTTP server...");
+        LOGGER.info("WebServer or MCP enabled in settings, starting HTTP server...");
         setEnabled(true);
     } else {
-        LOGGER.info("WebServer disabled in settings, NOT starting HTTP server (saves ~10KB RAM)");
+        LOGGER.info("WebServer and MCP disabled in settings, NOT starting HTTP server (saves RAM)");
         setEnabled(false);
     }
 
@@ -268,11 +271,16 @@ void WebServerService::setEnabled(bool enabled) {
     lock.lock();
     
     if (enabled) {
+        // Start unconditionally if explicitly requested
         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();
         }
     }
@@ -1035,13 +1043,22 @@ esp_err_t WebServerService::handleApiGet(httpd_req_t* request) {
 
 // API POST dispatcher - all POST endpoints require authentication
 esp_err_t WebServerService::handleApiPost(httpd_req_t* request) {
+    const char* uri = request->uri;
+
+    // Route MCP endpoints unauthenticated
+    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);
     }