fix(explore): update browser tab title with chart name

[guechhouth]

SUMMARY

This PR updates the browser tab title to display the chart name when viewing a chart in Explore view. The implementation:

• Sets the document title to the chart's slice name when a chart is loaded
• Resets the title back to "Superset" when navigating away from the chart
• Uses React's useEffect cleanup pattern to prevent memory leaks
• Follows the same pattern already used by the Dashboard page

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

video link: https://youtu.be/UCzXr4uxt58

TESTING INSTRUCTIONS

1. Navigate to a saved chart in Explore view
2. Verify the browser tab title updates to show the chart name
3. Navigate away from the chart (e.g., go to dashboard list)
4. Verify the browser tab title resets to "Superset"
5. Open a different chart and verify the title updates to the new chart name

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API: Fixes Issue #7 - Browser tab title not updating to chart name when opening charts #20
• Removes existing feature or API