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/package-lock.json

@@ -11,6 +11,7 @@
         "@react-pdf/renderer": "^4.3.2",
         "axios": "^1.6.7",
         "dexie": "^4.4.2",
+        "heic-to": "^1.4.2",
         "leaflet": "^1.9.4",
         "lucide-react": "^0.344.0",
         "mapbox-gl": "^3.22.0",
@@ -5827,6 +5828,12 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/heic-to": {
+      "version": "1.4.2",
+      "resolved": "https://registry.npmjs.org/heic-to/-/heic-to-1.4.2.tgz",
+      "integrity": "sha512-y69thwxfNcEm2Vk8lbOD/cMabnvMJyOREfJYiCHcXCDqlfcPyJoBhyRc8+iDe1B95LRfpbTOpzxzY1xbRkdwBA==",
+      "license": "LGPL-3.0"
+    },
     "node_modules/hsl-to-hex": {
       "version": "1.0.0",
       "license": "MIT",