Per-pad FX chain, animated toggles, GR meter, simplified master panel

- FX moved from master bus to per-pad processing:
  each pad has its own Filter, Distortion, EQ, Compressor, Reverb
  via DrumPad::applyPadFx() with temp buffer rendering
- FxPanel now edits the selected pad's FX parameters
- Animated toggle switches with smooth lerp transition and glow
- Per-pad compressor GR meter connected to FxPanel display
- Master panel simplified: Volume/Tune/Pan + Limiter toggle + VU meter
- Master bus chain: Vol/Pan → Output Limiter (0dB brickwall) → VU
- Pointer glow reduced to half intensity (4 layers, narrower spread)
- Smooth 8-layer arc glow with exponential opacity falloff

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Source/MasterPanel.h

@@ -13,6 +13,7 @@ public:
     float getMasterVolume() const { return (float) volumeSlider.getValue(); }
     float getMasterTune()   const { return (float) tuneSlider.getValue(); }
     float getMasterPan()    const { return (float) panSlider.getValue(); }
+    bool  isLimiterEnabled() const { return limiterToggle.getToggleState(); }
 
     VuMeter& getVuMeter() { return vuMeter; }
 
@@ -20,6 +21,10 @@ private:
     juce::Slider volumeSlider, tuneSlider, panSlider;
     juce::Label  volumeLabel, tuneLabel, panLabel;
     juce::Label  masterTitle { {}, "MASTER" };
+
+    juce::ToggleButton limiterToggle;
+    juce::Label limiterLabel { {}, "LIMITER" };
+
     VuMeter vuMeter;
 
     void setupKnob (juce::Slider& s, juce::Label& l, const juce::String& name,