Add a sub-menu to the shuffle playlist menu to decide how to shuffle.

[Vinzzzze]

Change the menu Shuffle playlist (mainwindow ui) to offer three shuffle modes :

• track based shuffle (the actual playlist shuffle mode)
• album based shuffle : shuffle the playlist by album and make the album played in the track number order
• grouped track shuffle : keep the grouped tracks together, other tracks and distinct track group are shuffled.

Correct what I consider as an issue : when playing a playlist with a mode shuffle grouped, the tracks are played in the order they have in the playlist. Grouped tracks must be played following the track number order.

Update mainwindow for updating the menus
Update playlist to make the ReshuffleIndices reusable for both Reshuffling indices when playing in shuffle mode and when shuffling the playlist from the menu. I left some commented code with a TODO mark for some code linked to another PR to remind me what to do when I will merge one branch in the other.
Update the playlistmanager and it's interface to handle the choice we can now make while shuffling a playlist.
Add the translations for the created menu

Summary by CodeRabbit

• New Features
  • Added a Shuffle playlist submenu with three mutually-exclusive modes: Single track as random element, Album as random element, and Grouped tracks as random element (existing Ctrl+H preserved for the single-track mode).
• Behavior Updates
  • Shuffle is now mode-aware.
  • Album and Grouped modes keep album/group boundaries and preserve disc/track ordering within the selected album or group while randomizing the chosen units.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/playlist/playlist.h`:
- Around line 370-371: The ReshuffleIndices function declaration is missing a
comma between the shuffle_mode parameter and the const bool
album_keep_track_order parameter. Add a comma after shuffle_mode to fix the
syntax error in the parameter list.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

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Run ID: 41daddfc-5ae5-49f0-b363-483a4ac1c5fa

📥 Commits

Reviewing files that changed from the base of the PR and between ba28391 and bf6d7b9.

📒 Files selected for processing (8)

• src/core/mainwindow.cpp
• src/core/mainwindow.h
• src/core/mainwindow.ui
• src/playlist/playlist.cpp
• src/playlist/playlist.h
• src/playlist/playlistmanager.cpp
• src/playlist/playlistmanager.h
• src/playlist/playlistmanagerinterface.h

🚧 Files skipped from review as they are similar to previous changes (5)

• src/playlist/playlistmanager.h
• src/playlist/playlistmanagerinterface.h
• src/core/mainwindow.ui
• src/core/mainwindow.h
• src/core/mainwindow.cpp