feat(image-engine): add Sharp wrapper with 14 image operations

Operations: resize, crop, rotate, flip, convert, compress, strip-metadata,
brightness, contrast, saturation, color-channels, grayscale, sepia, invert.
Includes format detection, MIME mapping, metadata parsing, and engine orchestrator.

packages/image-engine/vitest.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    globals: true,
+  },
+});