Add bcrypt_password validation to password reset and update endpoints:
- Add validation tag to PasswordReset.NewPassword struct field
- Add validation tag to UserPassword.NewPassword struct field
- Add c.Validate() calls in both handlers
- Fix off-by-one error in bcrypt_password validator (use <= 72 not < 72)
Password requirements: min 8 chars, max 72 bytes (bcrypt limit)