[UI] Absolute layout in GuiPanel breaks WindowBuilder compatibility

[AmlanDalai]

Hello, I am exploring this codebase as part of GSoC 2026 preparation and have identified the following issue.

Problem

GuiPanel currently uses setLayout(null) with hardcoded setBounds() coordinates for all 9 navigation buttons. This causes two problems:

1. UI does not respond to window resizing — breaks on different screen resolutions commonly used in life science workstations
2. Eclipse WindowBuilder can only parse 2 of 9 components in Design view, making visual UI editing impossible

Evidence

Opening GuiPanel.java in Eclipse WindowBuilder Design view shows only:

• label - "Active Segmentation"
• button - "Select Filters"

The remaining 7 buttons are invisible to WindowBuilder because they are created inside a factory method addButton() rather than as named fields.

Proposed Fix

• Replace setLayout(null) with BorderLayout at panel level
• Replace button grid with GridBagLayout
• Declare each button as a named field for WindowBuilder compatibility
• Each button uses its own GridBagConstraints instance

Related

This is directly aligned with the GSoC 2026 project idea: "streamline and simplify the existing UI implementation using WindowBuilder"