feat: use local mdk packages with useProducts hook

- Update .gitignore to allow local-packages/*.tgz
- Include local @moneydevkit/core and @moneydevkit/nextjs packages
- Update package.json to reference local packages
- Update Dockerfile to copy local-packages directory

Author: NatElkins

.gitignore

@@ -19,6 +19,7 @@ coverage
 .idea
 .vscode
 *.tgz
+!**/local-packages/*.tgz
 .secrets
 .envrc
 .direnv

mdk-nextjs-demo/Dockerfile

@@ -9,8 +9,9 @@ WORKDIR /app
 # Install curl and jq for healthchecks and JSON manipulation
 RUN apk add --no-cache curl libc6-compat jq
 
-# Copy package files
+# Copy package files and local packages
 COPY package.json package-lock.json* ./
+COPY local-packages ./local-packages
 
 # Install dependencies
 RUN npm install