chore(ws): Add support for PF utility classes

[jenny-s51]

Summary

Adds support for PatternFly utility classes.

Changes

• Added @patternfly/patternfly/patternfly-addons.css import to App.tsx
• Enables usage of PatternFly utility classes throughout the application (spacing, display, text, sizing, flex, background, etc.)

Benefits

• Provides access to PatternFly's comprehensive utility class system
• Prevents inline/custom CSS for common styling patterns

Testing Instructions

1. Add className="pf-v6-u-text-color-brand" to the Title component on line 54 of workspaces/frontend/src/app/App.tsx:

   <Title headingLevel="h2" size="3xl" className="pf-v6-u-text-color-brand">
     Kubeflow Notebooks 2.0
   </Title>

2. Save the file and verify the application title text appears in blue (PatternFly brand color)
3. Remove the test class when verification is complete

Related

• Closes: [TASK] Support Patternfly Utility Classes #420
• Related: improve: UX Enhancements in workspace summary #473

[jenny-s51]

/assign

[paulovmr]

/ok-to-test

[paulovmr]

/lgtm

[ederign]

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ederign

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