Fix Media Manager critical syntax errors and enforce ES5 architecture

- Resolved persistent 'SyntaxError: Unexpected token class' by refactoring 'MediaState' and 'UI' classes in MediaManager.html to standard ES5 function constructors.

- Resolved 'SyntaxError: Unexpected identifier src' by rewriting 'createCard' to use 'document.createElement' instead of template strings for dynamic media elements.

- Consolidated script tags in MediaManager.html to prevent Apps Script parser merge issues.

- Updated docs/ARCHITECTURE.md and MEMORY.md to formally document client-side constraints (No ES6 classes, strict DOM manipulation for media).

- Note: Google Drive video animate-on-hover functionality is implemented but currently pending verification/fix.

MEMORY.md

@@ -40,5 +40,9 @@ This project (`product_inventory`) integrates Google Sheets with Shopify. It ser
         1. Sanitize with `Utilities.newBlob()`.
         2. Fallback to **Advanced Drive Service** (`Drive.Files.create` / `v3`) if standard creation fails.
 - **Video Previews**:
-    - HTML5 `<video>` tags often fail with standard Drive download URLs due to auth/codec issues.
-    - **Strategy**: Use an `<iframe>` embedding the `https://drive.google.com/file/d/{ID}/preview` URL. This leverages Google's native player for reliable auth and transcoding.
+- **Video Previews**:
+    - Use `document.createElement('video')` to inject video tags. Avoid template strings (`<video src="...">`) as the parser sanitizes them aggressively.
+    - Fallback to `<iframe>` only if native playback fails.
+- **Client-Side Syntax**:
+    - **ES5 ONLY**: Do not use `class` in client-side HTML files. The Apps Script sanitizer often fails to parse them. Use `function` constructors.
+