Bug: New tab button disappears when many tabs are open

[camiicode]

Problem:
When a large number of note tabs are created,
the "new tab" button becomes inaccessible or disappears
from the visible area.

Even when horizontal scrolling is available,
the button cannot be reached, preventing the user
from creating new notes.

This creates a hard UX blocker.

Expected behavior:
The "new tab" button should always remain visible
and accessible, regardless of the number of open tabs.

Possible cause:
The tabs container grows without a maximum width,
causing the button to be pushed outside the viewport.

Steps to reproduce:

1. Open multiple note tabs.
2. Continue adding tabs until the container overflows.
3. Observe that the "new tab" button is no longer visible.

Acceptance criteria:

• Tabs container has a maximum width.
• "New tab" button remains visible at all times.
• Button can be fixed or floating at the right edge.
• Horizontal scrolling does not hide critical actions.