[fix] Keep Launch visible and group Reset below settings - #187

The expanded start menu can push Launch below the visible area. Keep Launch in a fixed footer while permissions and settings scroll above it, and size the window to its laid-out content up to the display’s available height. Preserve the settings’ scroll position when sizing the window.

Reset lives in its own section below Immersive, with an icon, a Factory reset title, and a brief description. Its button uses red text and the standard border at rest, then fills red on hover. The section stays in the scrolling content. Return-key launch, typed reset confirmation, permissions, and VM settings retain their existing behavior.

Validation:

• Full make test passed after merging current main: 275 native tests, 153 guest Python tests, and the shell/storage checks. The optional virtio-pinch ABI and staged-QEMU lock-inheritance checks were skipped because their binaries were unavailable.
• The start-menu regression test verifies that Launch stays outside the scroll view and Reset follows the integrations inside it, with Return-key launch preserved.
• The rebuilt local app was opened and visually checked for the fixed Launch footer, the Reset section below Immersive, and the final button appearance.
• git diff --check passed.