Consolidate component theming by overriding PF global tokens

[jenny-s51]

As we handle more deeply nested component patterns and continue to expand component coverage, we need to refactor the theming stylesheet to streamline the implementation and maintenance of component theming.

A key aspect of this refactor will be mapping existing PF -> MUI component-level overrides to PF semantic global tokens.

Benefit:

• Makes nested components work automatically (they inherit globals)
• Reduces dev effort for future component theming
• Consistency across components

Sub-tasks for this issue:

See linked sub-issues below this PR description for highest-impact architectural tasks (addressed in #77).

Cleanup (to be addressed as a follow-up to #77):

• Create Table of Contents with component sections
• Eliminate Magic Numbers / Extract to named tokens
• Standardize variable naming
• Remove hardcoded MUI Values / reference theme variables instead

Acceptance Criteria

• Global PF token overrides consolidated in one section at top of file
• Clear table of contents for global tokens, semantic tokens, and PF component-specific tokens
• No hardcoded color/shadow/spacing values

References

• MUI Default Theme
• MUI CSS Theme Variables
• https://www.patternfly.org/design-foundations/theming/#patternfly-themes