[TASK] Replace Session-Based Lock Period Display with Real Estimated Timespan

[monaiuu]

Description

The current dApp displays lock periods in sessions, which can be confusing and unclear for users when they are transacting on Tangle. To improve clarity and user experience, let's update the lock period display to show a real estimated timespan (e.g., "7 days" or "10 hours") instead of sessions.

Acceptance Criteria:

• Ensure the estimated timespan calculation is based on the session duration and the number of sessions required for the lock.
• Replace the current session-based lock period display with an estimated timespan format (e.g., "7 days", "10 hours").
• Update the UI to reflect the new format clearly and consistently across all relevant sections of the dApp.