fix(security): Update dependencies and remove unused files

- Update python-jose to 3.3.1
- Update python-multipart to 0.0.20
- Remove unused frontend_backup folder

Resolves security vulnerabilities identified by Dependabot.

Author: Gunjan KHANDPUR

backend/requirements.txt

@@ -1,9 +1,9 @@
-# Core dependencies
+# Core dependencies
 fastapi==0.115.6
 uvicorn==0.32.1
 python-dotenv==1.0.0
 pydantic==2.11.0
-python-multipart==0.0.16
+python-multipart==0.0.20
 
 # HTTP client
 httpx==0.28.1
@@ -16,7 +16,7 @@ pandas==2.2.3
 cachetools==5.3.0
 
 # Security
-python-jose[cryptography]==3.3.0
+python-jose[cryptography]==3.3.1
 passlib[bcrypt]==1.7.4
 
 # Database (optional, for future use)