#179- sanitize path outputs of template created and filled

[Cubix33]

Closes #179

🚀 Description

Fixes path traversal vulnerabilities and secures temporary file storage. Replaced insecure string slicing with pathlib for safe filename extraction, and implemented tempfile to securely manage intermediate templates outside the project root.

🛠️ Changes Proposed

• src/file_manipulator.py: Switched to tempfile.mkstemp() to securely generate _template.pdf in the OS temp directory.
• src/filler.py: Replaced [:-4] with pathlib.Path().stem and added auto-routing for final PDFs into an isolated outputs/ directory.

✅ PR Checklist

• Path traversal vulnerability mitigated.
• outputs/ directory dynamically created if missing.
• Temporary template files are no longer stored in the project root.