feat: add support for JXL, Camera RAW, ICO, TGA, PSD, EXR, HDR image formats

Extends the platform to handle 7 new image format families alongside
the existing AVIF support gap-fill. Uses the established HEIC decoder
pattern (CLI decode → PNG → Sharp) for formats Sharp can't handle
natively: Camera RAW via dcraw_emu/LibRaw, PSD/TGA/EXR/HDR via
ImageMagick. JXL and ICO are Sharp-native. Adds server-side preview
for non-browser-displayable formats and JXL as a new convert output
target. All 27 validateImageBuffer callers updated with filename for
extension-based format detection.

packages/image-engine/src/engine.ts

@@ -73,6 +73,7 @@ const FORMAT_MAP: Record<string, string> = {
   heif: "avif",
   tiff: "tiff",
   gif: "gif",
+  jxl: "jxl",
 };
 
 /**