feat(journey): convert HEIC/HEIF uploads to JPEG for cross-platform compatibility

HEIC is an Apple-only format not recognised as an image by many browsers
and platforms. heic-to (lazy-loaded) now converts HEIC/HEIF files to JPEG
before upload in both the gallery and entry editor photo pickers.
Embedded metadata (EXIF, GPS) may be lost during conversion — documented
in the Journey Journal wiki page.

client/src/utils/convertHeic.ts

@@ -0,0 +1,11 @@
+export async function normalizeImageFile(file: File): Promise<File> {
+  const { isHeic, heicTo } = await import('heic-to')
+  if (!(await isHeic(file))) return file
+  const blob = await heicTo({ blob: file, type: 'image/jpeg', quality: 0.92 })
+  const jpegName = file.name.replace(/\.(heic|heif)$/i, '.jpg')
+  return new File([blob], jpegName, { type: 'image/jpeg' })
+}
+
+export async function normalizeImageFiles(files: FileList | File[]): Promise<File[]> {
+  return Promise.all(Array.from(files).map(normalizeImageFile))
+}