Improve ui with colors and ux

[davidt-gh]

What does this PR change?

• Implements a comprehensive UI/UX refresh for the OpenCost application.
• Introduces a new Material-UI theme with a modern color palette, typography (Inter font), and updated component styles.
• Redesigns key UI components including the Header, Sidebar Navigation, Footer, Subtitle, and Warnings.
• Adds a new DashboardWelcome component to enhance the landing experience.
• Incorporates global CSS improvements for scrollbars, tooltips, tables, and adds new animation utilities.

Does this PR relate to any other PRs?

• No

How will this PR impact users?

• Users will experience a significantly modernized, professional, and visually appealing user interface.
• Improved readability, navigation, and overall user experience due to consistent design and updated aesthetics.

Does this PR address any GitHub or Zendesk issues?

• Closes N/A

How was this PR tested?

• Manually tested by running the application in a development environment and visually verifying all updated components and pages.

Does this PR require changes to documentation?

• No, this PR focuses solely on UI/UX improvements and does not alter functionality or introduce new features requiring documentation updates.

Have you labeled this PR and its corresponding Issue as "next release" if it should be part of the next OpenCost release? If not, why not?

• No, this is a UI improvement and not a new feature or bug fix directly tied to a release cycle.

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