feat(shared): extract client/server pure helpers into @jerapah-flow/shared

Share profile merge, workflow filename/path helpers, HTTP_METHODS (with OPTIONS), and isPlainObject so web and server stop drifting. Core script sandboxes keep local isPlainObject copies.

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/shared/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "@jerapah-flow/shared",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "exports": {
+    ".": "./src/index.js"
+  }
+}