[26.3] PI Objective 1: Handle styling of MMGIS core and plugins

[BhattaraiSijan]

Motivation:

Enable projects like disasters and air4us to use MMGIS core along with shared plugins while applying distinct visual styles (e.g., themes, typography, branding) without modifying any code.

Description:

Redesign MMGIS styling architecture to support a scalable, themeable system across both core and plugins. This should also work well with reusable components library being developed by Dashboard team.

Acceptance Criteria:

• Core and plugin styles consume values from a centralized token system (no hardcoded styling values)
• Create a disaster theme file that successfully overrides default styling (e.g., colors, fonts)
• A working prototype demonstrating themeability using few Plugins

Definition of Done:

• MMGIS dashboards support theming via a configurable theme file
• Core and plugins consistently use shared design tokens
• Compatibility with Reusuable Components Library (and it's design tokens)