Refactor and expand the Effects view UI.

Added many new sliders, toggles and numeric inputs (hue, saturation, temperature, vibrance, color-balance tabs, exposure, gamma, highlights/shadows/blacks/whites, dehaze, clarity, grain, sharpen, vignette, blur, posterize, solarize, pencil sketch, presets UI, etc.).
Add gradient brushes and UI polish (spacing, sizes, brush resources). Update code-behind and core effect classes (ImageEffectConfig, ImageEffectsHelper, EffectsView.axaml.cs) to support the new controls, parameters and preset handling.

Fixes Issue #296

Author: mghe01