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/interfaces/IShopifyMediaService.ts

@@ -0,0 +1,4 @@
+export interface IShopifyMediaService {
+  stagedUploadsCreate(input: any[]): any
+  productCreateMedia(productId: string, media: any[]): any
+}