[DESIGN] Inline Font and Color declarations bypass shared ASCommon constants

[AmlanDalai]

Problem

ASCommon interface already defines shared UI constants (largeFONT,
labelFONT, mediumFONT, buttonBGColor etc.) but multiple panels
ignore them and declare inline values directly:

UIPanel.java — 6 inline Font declarations using "Tahoma" font
family, inconsistent with ASCommon which uses "Arial" throughout.

SessionGUI.java — redefines labelFONT locally, shadowing ASCommon.

VisualizationPanel.java — redefines buttonBGColor locally with the
same value already defined in ASCommon.

FeaturePanel.java — 3 inline Font declarations.

ViewFilterOutputPanel.java — 4 inline Font declarations.

FilterPanel.java — 2 inline Color declarations.

Impact

1. Font inconsistency — UIPanel uses Tahoma while all other panels
   use Arial, creating a visually inconsistent UI
2. Maintenance burden — a font or color change requires editing
   multiple files instead of one
3. Risk of divergence — locally redefined constants can silently
   drift from the shared values over time

Proposed Fix

• Extend ASCommon with a complete, well-documented set of UI constants
• Replace all inline Font and Color declarations with shared constants
• This makes the entire UI consistent and maintainable from one place

Related

Directly aligned with the GSoC 2026 goal of consistent visual
design across all UI panels.