[Remove Vuetify from Studio] Add / remove admin privileges dialogs

[rishabhjain1712]

Fixes #5441

Summary

This PR refactors the User Privilege Modal to remove dependency on Vuetify (v-dialog, v-form, etc.) and migrate it to use Kolibri Design System (KDS) components such as KModal, KTextbox, and KButton.

• Replaced v-dialog with KModal for modal rendering.
• Removed v-form in favor of generateFormMixin for validation handling.
• Updated modal actions (Add/Remove privilege, Cancel) to work with KDS event handling (@submit, @cancel).
• Ensured all existing logic (confirmAction, close, onSubmit) and state management remain functional.
• Confirmed that the modal opens and closes correctly, validates input, and performs privilege actions as before.
• Minor visual differences are expected due to use of KDS, but no functional regressions.

Manual Verification

• Opened the User Privilege Modal in the Admin > Users section.

• Verified that:

  • Modal renders without freezing or layout issues.
  • Input field validation works correctly via generateFormMixin.
  • “Cancel” and “Add/Remove Privilege” buttons perform expected actions.
  • Confirmed no console errors and all API calls are working.

Screenshots:
(Already included above 👆)

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References

• Related issue: Refactor Vuetify usage in user privilege modal to KDS equivalents ([Remove Vuetify from Studio] Add / remove admin privileges dialogs #5441 )([Remove Vuetify from Studio] Add / remove admin privileges dialogs #5441)

• Internal discussion: Migration to KDS components and removal of Vuetify dependencies

• Component references:

  • kolibri-design-system v5.2.2
  • vue v2.7.16

Reviewer Guidance

To test these changes:

1. Navigate to the User Management section in the app.

2. Open a user’s privilege modal.

3. Verify:

   • Modal opens normally with no freezing.
   • Input validation behaves as expected.
   • Cancel and Confirm buttons close or submit the modal correctly.
   • Snackbar notifications appear after successful actions.

4. Ensure no UI regressions or console errors occur.

[MisRob]

Just quickly from the code I don't think that snackbar was displayed before or was it? Please double-check, and if that's the case, remove this logic.

[rishabhjain1712]

Sure, actually I was referring to changeUserPassword.vue so added it. Will remove

[MisRob]

Thank you @rishabhjain1712, we will assign a reviewer next week.

Meanwhile see my note on user experience, and also I noticed that tests check is failing - needs to be fixed.