Refactor GUI layout to remove Progress tab and surface progress on the main screen

[peter7775]

Summary

The current Fyne GUI keeps progress information in a separate Progress tab, while the main practice flow lives in Practice. This makes the most important learning feedback less visible during normal use.

Problem

• Progress is hidden behind a tab instead of being visible during practice.
• The learning loop is split across multiple views.
• The current layout increases context switching for the user.

Proposed change

• Move the progress bar and compact progress summary onto the main practice screen.
• Keep detailed stats below the main content or in a collapsible panel instead of a separate tab.
• Reduce the number of top-level tabs if they are no longer needed.

Acceptance criteria

• Progress bar is visible on the main screen at all times during practice.
• Current score, correct answers, wrong answers, and attempts are visible without changing tabs.
• The practice flow works without opening a separate Progress tab.
• Layout remains usable at the current desktop target size.

Notes

Relevant area: internal/gui/app.go / app-2.go build and refresh flow.