UI polish: amber theme, smooth spectrum, MIDI LED, VU tuning

- Rename section labels: COMPRESSOR → COMPRESSION, AUTO-PAN → PANNING
- Replace spectrum analyzer bars with smooth gapless filled wave
- Use gold (#c59c07) for wave/spectrum strokes and piano roll active keys
- Amber CRT-style patch LCD with dark background and gold dot-matrix text
- Add MIDI signal LED with glow between semi and scale controls
- Reduce VU meter sensitivity (5x → 1.5x) and match amber gradient theme
- Add subtle glow behind section and sub-section boxes
- Fix Compressor.h class name and PluginProcessor include to match

Source/PluginProcessor.h

@@ -69,6 +69,11 @@ public:
         return midiNote >= 0 && midiNote < 128
                && activeNotes[midiNote].load(std::memory_order_relaxed);
     }
+    bool isAnyNoteActive() const {
+        for (auto& n : activeNotes)
+            if (n.load(std::memory_order_relaxed)) return true;
+        return false;
+    }
 
     int getTransposeSemitones() const;
 
@@ -88,7 +93,7 @@ private:
     static constexpr int maxVoices = 16;
 
     Distortion distortion;
-    Compressor compressor;
+    Compression compression;
     Limiter limiter;
     Delay delay;
     ReverbFX reverbFX;