fix : add dark mode text color to Dashboard tag modal inputs and labels

[tmdeveloper007]

Closes #1886

Summary of What Has Been Done

Added missing text-main dark mode color class to the inline tag modal in frontend/src/pages/Dashboard.jsx, which is shown when users select tags from their profile.

Changes Made

• Added text-main to the "Select Tags" heading for proper dark mode text color
• Added text-main to each tag label checkbox so labels are readable in dark mode
• Added full dark mode styling (border-soft, bg-transparent, dark:bg-slate-800, dark:text-white, dark:placeholder-slate-500) to the custom tag text input

Impact it Made

• Tag labels and the custom tag input are now readable in dark mode
• The inline tag selection modal now respects the app theme consistently with other components
• Prevents invisible or low-contrast tag labels when users open the tag modal in dark mode

Note: Please assign this PR to the tmdeveloper007 account.