Feature: Robust Google Photos Integration & Media Hardening

- Implemented Google Photos Picker with Session API.
- Fixed 403 Forbidden errors by adding OAuth headers to download requests.
- Implemented MediaHandler resilience:
  - 3-Step Import (Save to Root -> Verify Folder -> Move).
  - Advanced Drive API Fallback (v3/v2) for file creation.
  - Blob Sanitization (Utilities.newBlob) to fix server errors.
- Enabled Advanced Drive Service in ppsscript.json.
- Updated Documentation (MEMORY.md, ARCHITECTURE.md) with findings.

docs/ARCHITECTURE.md

@@ -118,3 +118,26 @@ We use **Husky** and **lint-staged** to enforce quality standards at the commit
 
 Classes (like `Product`) should accept an `ISpreadsheetService` in their constructor. This allows providing the Mock service during tests to verify logic without touching real Google Sheets.
 
+
+### 7. Media Manager (`src/mediaHandlers.ts`, `src/MediaSidebar.html`)
+
+We implemented a "Sidebar-First" architecture for product media to handle the complexity of Google Picker and Shopify Sync.
+
+#### Frontend (`MediaSidebar.html`)
+- **Glassmorphism UI**: Uses modern CSS for a premium feel.
+- **Polling**: Since the sidebar can't listen to Sheet events directly efficiently, it polls `getMediaState(sku)` to detect when the user selects a different product row.
+- **Google Picker API**:
+    - Uses the **New Google Photos Picker** (Session-based) for selecting photos.
+    - Uses the **Google Drive Picker** (Legacy) for selecting existing Drive files.
+    - Handles OAuth token passing securely from the server side (`google.script.run`).
+
+#### Backend (`mediaHandlers.ts`)
+- **Import Strategy**:
+    - **Safe Zone**: Files are first downloaded/copied to the Drive Root to ensure we have the asset.
+    - **Move**: Then they are moved to the organized SKU folder (`/Product Photos/[SKU]/`).
+    - **Resilience**: The file creation logic tries multiple methods (Standard `DriveApp`, Sanitized Blob, Advanced `Drive` API) to handle the notoriously fickle nature of UrlFetchApp blobs.
+- **Shopify Sync**:
+    - `MediaService` manages the state.
+    - Calculates checksums to avoid re-uploading duplicate images.
+    - Uses Shopify's "Staged Uploads" -> "Create Media" mutation flow.
+