[YM!] Veil Iris Lights Compat (VILC)

Added

• Initial NeoForge 1.21.1 support
• Veil shader capture and Iris shader-program translation
• Vertex and fragment shader integration into Iris G-buffer programs
• Opaque Veil effect support
• Translucent Veil effect support through EntitiesTrans
• Dithering fallback for translucent effects
• Iris shadow-pass integration for Veil-rendered geometry
• Shader cache with automatic invalidation after shaderpack reloads
• Graceful fallback to standard Veil rendering when Iris shaders are disabled
• Bundled GLSL Transformer runtime