feat(mcp): restore MCP system with native log.h

- MCP 3.3K LOC: McpSystem 1899 + McpHandler 1029 + McpScreensaver + 2 apps
- Uses native tactility/log.h TAG macros, no old Logger.h
- DisplaySettings McpScreen enum, WebServer coexistence (MCP enabled starts HTTP)
- DisplayIdle: startMcpScreensaver + isDeviceCharging + lock inversion fix 3629ffef
- LVGL 512K PSRAM cache retained from previous perf patch
- Audio kept upstream es8311-module per note we might not need custom

Tactility/Source/settings/McpSettings.cpp

@@ -0,0 +1,72 @@
+#include <Tactility/settings/McpSettings.h>
+#include <Tactility/file/PropertiesFile.h>
+#include <Tactility/file/File.h>
+#include <tactility/log.h>
+
+constexpr auto* TAG = "McpSettings";
+#include <Tactility/Paths.h>
+#include <map>
+#include <string>
+
+namespace tt::settings::mcp {
+
+
+static std::string getSettingsFilePath() {
+    return getUserDataPath() + "/settings/mcp.properties";
+}
+
+constexpr auto* KEY_MCP_ENABLED = "mcpEnabled";
+
+bool load(McpSettings& settings) {
+    auto settings_path = getSettingsFilePath();
+    if (!file::isFile(settings_path)) {
+        return false;
+    }
+    std::map<std::string, std::string> map;
+    if (!file::loadPropertiesFile(settings_path, map)) {
+        return false;
+    }
+
+    auto mcp_enabled = map.find(KEY_MCP_ENABLED);
+    settings.mcpEnabled = (mcp_enabled != map.end())
+        ? (mcp_enabled->second == "1" || mcp_enabled->second == "true")
+        : false;
+
+    return true;
+}
+
+McpSettings getDefault() {
+    return McpSettings{
+        .mcpEnabled = false
+    };
+}
+
+McpSettings loadOrGetDefault() {
+    McpSettings settings;
+    if (!load(settings)) {
+        settings = getDefault();
+        if (!save(settings)) {
+            LOG_W(TAG, "Failed to save default MCP settings");
+        }
+    }
+    return settings;
+}
+
+bool save(const McpSettings& settings) {
+    std::map<std::string, std::string> map;
+    map[KEY_MCP_ENABLED] = settings.mcpEnabled ? "true" : "false";
+
+    auto settings_path = getSettingsFilePath();
+    if (!file::findOrCreateParentDirectory(settings_path, 0755)) {
+        LOG_E(TAG, "Failed to create parent dir for %s", settings_path.c_str());
+        return false;
+    }
+
+    if (!file::savePropertiesFile(settings_path, map)) {
+        LOG_E(TAG, "Failed to save MCP settings to %s", settings_path.c_str());
+        return false;
+    }
+    return true;
+}
+
+} // namespace