Fix last_modified

[adithya-naik]

Fix Last Activity Calculation per Repository Item

What does this PR do?

Closes #440

This pull request fixes how the “Last Activity” time is calculated and displayed for each repository item.

Previously, the relative time logic was defined inside the component, which could lead to incorrect or inconsistent behavior across repository items.

This change ensures that each repository correctly computes and displays its own relative last-modified time.

---

Why is this change needed?

• Hooks should not be defined inside components.
• dayjs.extend(relativeTime) should be initialized once, not on every render.
• Ensures React hook rules are followed.
• Improves code clarity and correctness.

---

What was changed?

• Moved dayjs.extend(relativeTime) to module scope.
• Extracted useLastModified into a proper custom hook.
• Ensured lastModified updates correctly when repository.last_modified changes.

---

Example

All repository items now correctly display their respective relative last activity times such as:

“2 years ago”

based on their individual last_modified values.

---

Technical Notes

• No new dependencies added
• No UI changes apart from fixing incorrect behavior
• Fully backward-compatible

---

Checklist

• React Hooks rules followed
• Cleaner component structure
• Accurate per-repository last activity display
• No breaking changes