docs: update ui base path configuration file path

[NithinU2802]

Which problem is this PR solving?

• Resolves [chore]: Documentation references Vite configuration file path #4255

Description of the changes

• To update the outdated vite configuration file path in CONTRIBUTING.md.
• Replaced jaeger-ui/jaeger-ui/vite.config.js with packages/jaeger-ui/vite.config.mts to match current project structure.

How was this change tested?

• Verified that the referenced file exists at packages/jaeger-ui/vite.config.mts.
• Did review the documentation to ensure the updated path is accurate.

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/main/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully: make lint test

AI Usage in this PR (choose one)

See AI Usage Policy.

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes