feat(media): implement integrated media manager with sidebar and picker

- Implement DriveService and ShopifyMediaService for backend operations
- Create MediaSidebar.html with premium UI and auto-polling
- Integrate Google Picker API for robust file selection
- Orchestrate sync logic via MediaService (Drive -> Staged Upload -> Shopify)
- Add secure config handling for API keys and tokens
- Update ppsscript.json with required OAuth scopes
- Update MEMORY.md and README.md with architecture details

src/services/MockShopifyMediaService.ts

@@ -0,0 +1,29 @@
+import { IShopifyMediaService } from "../interfaces/IShopifyMediaService"
+
+export class MockShopifyMediaService implements IShopifyMediaService {
+  stagedUploadsCreate(input: any[]): any {
+    return {
+      stagedTargets: input.map(i => ({
+        url: "https://mock-upload.shopify.com",
+        resourceUrl: `https://mock-resource.shopify.com/${i.filename}`,
+        parameters: []
+      })),
+      userErrors: []
+    }
+  }
+
+  productCreateMedia(productId: string, media: any[]): any {
+    return {
+      media: media.map(m => ({
+        alt: m.alt,
+        mediaContentType: m.mediaContentType,
+        status: "PROCESSING"
+      })),
+      mediaUserErrors: [],
+      product: {
+        id: productId,
+        title: "Mock Product"
+      }
+    }
+  }
+}