fix : add missing dark mode text color to OnboardingModal tag button labels

[tmdeveloper007]

Summary of What Needs to be Done

The OnboardingModal component (likely in frontend/src/components/OnboardingModal.jsx) displays selectable tag buttons, but the selected tag button labels may not use the theme-aware text color class (text-main) consistently, causing poor contrast in dark mode.

Changes that Need to be Made

In the OnboardingModal component:

1. Locate the tag selection button/render section
2. Ensure selected tag buttons use text-main (or equivalent theme variable class) for their label text color
3. Ensure the hover state also respects theme colors

Impact that it would Provide

• Readable tag labels in dark mode
• Consistent dark mode experience from the onboarding flow
• Prevents invisible or low-contrast tag labels when users first sign up

Note: Please assign this issue to the tmdeveloper007 account.