Add HDF (Highlight Diffusion Filter) to the FX tab

The built-in lens filter, simulated the way it is done in Photoshop: pull the
highlights out with a hard contrast curve (out = 2.5*in - 1.5, black below 0.6),
Gaussian-blur that selection, then Screen it back over the photo at reduced
opacity. Screen against a near-black pixel is a no-op, so areas with no
highlight within the blur radius come back byte-identical while lit areas
spread their light.

One 0..10 knob drives both the radius (4%..1.9% of the width, ~10..50px at
2560 wide) and the opacity (0.15..0.5), matching the recipe's 15-50px radius
range. The extraction composes on top of the recipe colour matrix so a
monochrome look glows white instead of leaking the original colours back.

Runs in the Skia export engine only; the P5 native path is not wired into the
app (dev parity probe only), so it is left alone for now.

src/types/index.ts

@@ -54,6 +54,7 @@ export interface ColorAdjustments {
   colorChromeBlue: 'none' | 'weak' | 'strong'; // Chrome effect (Blue)
   dynamicRange: 'auto' | 100 | 200 | 400; // Fuji-style DR tone curve (auto/100 = no extra curve)
   sharpening: number; // 0 to 10 (output screen sharpen strength)
+  hdf?: number; // 0 to 10 (Highlight Diffusion Filter: glow on the highlights only)
   exposureCompensation: number; // -3 to +3 EV. Camera: AE bias (hardware). Library: 2^EV matrix gain.
 }