Fix: add all doctor schema fields to the Add Doctor form

• I added all the fields the form needs: name, age, sex, specialization, email, phone, license number, and availability.
• I arranged the fields in the exact order you asked for.
• I put a * on every required field label.
• The “Add to Directory” button stays off until all required fields are filled.
• It now checks that age is valid and email looks correct before saving.

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Before

After

Closes #139 (closed)