docs: add project documentation, memory, and setup guides

docs/SETUP.md

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+# Setup Guide
+
+## Local Development Environment
+
+1.  **Install Node.js**
+    This project uses `fnm` to manage Node versions.
+    ```powershell
+    # Install fnm (if not installed)
+    winget install Schniz.fnm
+    # Configure environment
+    fnm env --use-on-cd | Out-String | Invoke-Expression
+    # Install Node version
+    fnm use --install-if-missing 22
+    ```
+
+2.  **Install Dependencies**
+    ```bash
+    npm install
+    npm install -g @google/clasp
+    ```
+
+3.  **Clasp Login**
+    Authenticate with Google to allow pushing code.
+    ```bash
+    clasp login
+    ```
+
+## Google Sheets Configuration
+
+1.  **Create a Google Sheet** (or use existing).
+2.  **"vars" Sheet**:
+    Create a tab named `vars` with the following columns: `key`, `value`.
+    Add the following rows:
+    - `productPhotosFolderId`: ID of the Drive folder for photos.
+    - `shopifyApiKey`: Your Shopify API Key.
+    - `shopifyApiSecretKey`: Your Shopify API Secret.
+    - `shopifyAdminApiAccessToken`: The Admin API access token.
+    - `shopifyApiURI`: e.g., `https://your-store.myshopify.com`
+    - `shopifyLocationId`: Location ID for inventory.
+    - `shopifyCountryCodeOfOrigin`: Two-letter country code (e.g., `US`).
+    - `shopifyProvinceCodeOfOrigin`: Two-letter province code (e.g., `NY`).
+
+## Deployment
+
+1.  **Build**
+    ```bash
+    npm run build
+    ```
+
+2.  **Push to Apps Script**
+    ```bash
+    npm run deploy
+    ```
+
+3.  **Install Triggers**
+    Open the Apps Script editor (Extensions > Apps Script).
+    Run the `reinstallTriggers` function manually once to set up the automation.