[Fix] Update status not updating when game starts processing

[MateoGonzalezLourido]

<--- Put the description here --->
When a game was already updating, calling addToQueue again (e.g. from a background refreshLibrary with autoUpdate) would unconditionally send status: 'queued', overwriting the active update state on the frontend. The game would show "Queued" even though it was actively updating.
Changes

downloadqueue.ts: addToQueue no longer sends status: 'queued' if the element is currently being processed (isRunning() && currentElement matches the game). This preserves the real update state.
constants.ts: Updates no longer show 0% before progress data is available. The percentage is only shown once percent has a real value, so during the preparation phase it shows "Updating" instead of "Updating 0%"

Use the following Checklist if you have changed something on the Backend or Frontend:

• Tested the feature and it's working on a current and clean install.
• Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• Created / Updated Tests (If necessary)
• Created / Updated documentation (If necessary)

[MateoGonzalezLourido]

Until a game has updates, I can't test the fix; it should work.