feat(native-export): scaffold local Expo module + native decode/encode bench probe (P0)

Local Kotlin module modules/recipescam-export (autolinked via expo ./modules)
exposes decodeEncodeAsync — BitmapFactory decode -> JPEG q95 encode -> file,
all on Dispatchers.IO off the JS/main threads. EXPO_PUBLIC_BENCH=1 builds run
src/dev/nativeBenchProbe.ts: 3 timed decode+encode passes on the bundled
wallframe artwork plus a JS-timer gap check proving the JS thread never
blocks during native rendering. Legacy Skia engine untouched (reference).

modules/recipescam-export/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "recipescam-export",
+  "version": "0.1.0",
+  "description": "Native Kotlin photo export pipeline (decode/process/encode off the JS thread) for Recipescam.",
+  "main": "index.ts",
+  "license": "MIT",
+  "private": true
+}