Persist engine state in DAW projects, black monochrome panel, expand preset bank

- Save/load the engine's full parameter set alongside the preset index so
  knob and menu tweaks survive relaunching a song project
- Make the plugin panel black: top/surround laser border and bottom deck
  (rotary + nav keys) are now #000000
- Extend factory bank to 320 categorized presets and add LCD click-to-open
  preset category browser

Source/PluginEditor.h

@@ -29,6 +29,7 @@ private:
     void buildRootMenu();
     void updateLCD();
     void cyclePreset (int delta);
+    void openPresetMenu();
 
     SM26AudioProcessor& proc;
     MenuSystem menu;