feat: add file deduplication and hash checking for uploads

- Implemented SHA-256 hashing for uploaded files to enable deduplication.
- Added CheckHash method to verify if a file with the same hash already exists.
- Updated Upload method to reuse existing media assets if a duplicate is found.
- Introduced a new hash column in the media_assets table to store file hashes.
- Enhanced the upload process to include progress tracking and hash calculation.
- Modified frontend to check for existing files before uploading and to show upload progress.
- Added vuedraggable for drag-and-drop functionality in the content editing view.

frontend/portal/package.json

@@ -19,7 +19,8 @@
     "tailwindcss": "^4.1.18",
     "tailwindcss-animate": "^1.0.7",
     "vue": "^3.5.24",
-    "vue-router": "^4.6.4"
+    "vue-router": "^4.6.4",
+    "vuedraggable": "^4.1.0"
   },
   "devDependencies": {
     "@vitejs/plugin-vue": "^6.0.1",