Require phone number for volunteers

[Copilot]

This change makes the phone number field required for volunteers (mentors) when they create or update their profiles.

What Changed:

• Updated the MentorForm in coderdojochi/forms.py to make the phone field required by changing required=False to required=True

Impact:

• New volunteers must provide a phone number during registration
• Existing volunteers will be prompted to add their phone number when updating their profile
• Form validation will prevent submission without a phone number
• Bootstrap form rendering will automatically display visual indicators (asterisk) showing the field is required

Technical Notes:

• This is a form-level validation change only - the database model remains unchanged to maintain compatibility with existing data
• The change is consistent with other required fields in the form (gender, birthday, race/ethnicity)
• No database migration is needed since the model field already supports both populated and empty values

The implementation follows the principle of minimal changes while ensuring volunteers provide essential contact information for coordination and safety purposes.

Fixes #896.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[karbassi]

Review the onboarding flow and make sure that it’s very clear for the mentor that the email and the phone number are required.
Add a brief helper explaining why we use the email and why it’s required under the form field.

Be sure to update any UI for the volunteer.

@copilot

[Copilot]

@karbassi Unfortunately I hit an unexpected error while processing your comment. I've automatically reported this to GitHub.

You can ask me to try again later by mentioning me in a new comment.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: dcd8d439-f541-4837-8ab3-c9934ed13873

Sorry for the inconvenience!