Logging Project: Design a structured logging format (optional for now)

[CarolineMorton]

This does not need to happen now.

Goal: Move from Vec<String> to a richer log structure (for better future-proofing and to allow filtering).

Scope:

• Define a LogEntry struct (with timestamp, action, payload)
• implement serialisation to/from JSON
• Add filtering, grouping, or export options