Add DOCX upload to populate Final Script from a document

Uses mammoth to extract raw text from an uploaded .docx file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -20,6 +20,7 @@
     "docx": "^9.7.0",
     "dompurify": "^3.4.9",
     "express": "^4.19.2",
+    "mammoth": "^1.12.0",
     "react": "^19.0.0",
     "react-dom": "^19.0.0"
   },