Implement Multi-tenancy & Metadata-based Filtering (Storage)

[likinio365]

Description:
Currently, files from all companies are stored in the same global buckets in MinIO, leading to a lack of data isolation. We need to isolate data per company and inject metadata to quickly reject malicious files before they reach the ClamAV scanner.

Acceptance Criteria:

• The Express backend dynamically creates/uses buckets based on the user's companyid(as a String) during upload.
• Custom metadata (e.g., role, original extension) is attached to the file upon saving to MinIO.
• An intermediate step (Filter Node) is added in Node-RED to evaluate metadata (e.g., MIME type mismatch) and immediately reject suspicious files, bypassing ClamAV.