feat(saves): Add rolling saves and menu timestamps for better progress management

[arhaanjan]

This pull request adds several quality-of-life improvements to the savestate system, designed to prevent progress loss and provide users with more clarity.

Problem Solved

While working with savestates, it's easy to accidentally overwrite a crucial save or forget which slot contains recent progress. The existing system requires users to remember which F-key corresponds to which save, and there is no quick way to cycle through slots or see when a save was made. I personally experienced progress loss due to this, which inspired these changes.

Changes

This PR introduces two non-intrusive features, leaving the original Shift+F1/F1 functionality intact:

1. Rolling Save/Load Hotkeys:

   • Ctrl+S: A "quick save" hotkey that saves to the first empty slot. If all slots are full, it safely overwrites the oldest savestate, preserving more recent ones.
   • Ctrl+L: A "quick load" hotkey that instantly loads the most recent savestate, allowing for quick recovery from mistakes.

2. UI Timestamps:

   • The File > Save State and File > Load State menus now display the precise date and time of each save
   • (e.g., 1 (2025-09-17 01:15:11)), or (empty) if the slot has not been used.

These additions provide a faster and safer way to manage game progress without removing the classic method that existing users are familiar with.

[Arisotura]

there's something weird going with the commit, this reverts some of the recent commits to melonDS

[arhaanjan]

there's something weird going with the commit, this reverts some of the recent commits to melon
synced with the recent commits works fine

[v-fox]

there's something weird going with the commit, this reverts some of the recent commits to melon
synced with the recent commits works fine

You haven't answered why you've reverted 32d6f4a
This is a pretty great quality-of-life change in theory, so I wanted to patch it in my build, but now it's sus.