Initial commit: InstaLPEQ linear phase EQ plugin

Full-featured linear phase EQ with interactive graphical curve display.
FIR-based processing (8192-tap), 8 parametric bands, multi-platform
CI/CD (Windows/macOS/Linux), InstaDrums visual style.

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

Source/LookAndFeel.h

@@ -0,0 +1,50 @@
+#pragma once
+#include <JuceHeader.h>
+
+class InstaLPEQLookAndFeel : public juce::LookAndFeel_V4
+{
+public:
+    // Colour palette
+    static inline const juce::Colour bgDark      { 0xff1a1a2e };
+    static inline const juce::Colour bgMedium    { 0xff16213e };
+    static inline const juce::Colour bgLight     { 0xff0f3460 };
+    static inline const juce::Colour textPrimary  { 0xffe0e0e0 };
+    static inline const juce::Colour textSecondary { 0xff888899 };
+    static inline const juce::Colour accent       { 0xff00ff88 };
+
+    // Knob type property key
+    static constexpr const char* knobTypeProperty = "knobType";
+
+    InstaLPEQLookAndFeel();
+
+    void drawRotarySlider (juce::Graphics& g, int x, int y, int width, int height,
+                           float sliderPosProportional, float rotaryStartAngle,
+                           float rotaryEndAngle, juce::Slider& slider) override;
+
+    void drawButtonBackground (juce::Graphics& g, juce::Button& button,
+                               const juce::Colour& backgroundColour,
+                               bool shouldDrawButtonAsHighlighted,
+                               bool shouldDrawButtonAsDown) override;
+
+    void drawToggleButton (juce::Graphics& g, juce::ToggleButton& button,
+                           bool shouldDrawButtonAsHighlighted,
+                           bool shouldDrawButtonAsDown) override;
+
+    // Custom fonts
+    juce::Font getRegularFont (float height) const;
+    juce::Font getMediumFont (float height) const;
+    juce::Font getBoldFont (float height) const;
+
+    // Background texture
+    void drawBackgroundTexture (juce::Graphics& g, juce::Rectangle<int> area);
+
+    juce::Typeface::Ptr getTypefaceForFont (const juce::Font& font) override;
+
+private:
+    juce::Typeface::Ptr typefaceRegular;
+    juce::Typeface::Ptr typefaceMedium;
+    juce::Typeface::Ptr typefaceBold;
+
+    juce::Image noiseTexture;
+    void generateNoiseTexture();
+};