Fix Bottom Navigation Bar Disappearing in MediaDetailPagerFragment

Changes

• MediaDetailPagerFragment.kt: Removed the hideTabs() call in onCreateView to prevent hiding the bottom navigation bar when displaying media details, ensuring it remains visible as per the requirement.
• MainActivity.kt: Added showTabs() calls in the onBackPressed method for all navigation cases to ensure the bottom navigation bar is restored when navigating back from any fragment, providing a robust fallback.

Testing

• Navigated from Nearby to Explore > Map tab, clicked a picture to open the bottom sheet, and then clicked "Details" to view MediaDetailPagerFragment. Verified that the bottom navigation bar remains visible.
• Tested back navigation to ensure the navigation bar stays visible when returning to the Explore tab.
• Tested other navigation paths (e.g., Contributions and Bookmarks to media details) to confirm consistent visibility of the navigation bar.

Fixes #6316