As an experienced mobile app developer, I can assure you a well-crafted, user-friendly Flutter app that caters to all your requirements. With my expertise in Firebase Auth SDK, I'll ensure seamless integration of features like Google SSO, Microsoft SSO, and email-password authentication.
Having worked on various deployments for ios and android platforms, your project is well within my capabilities. Whether it's sign-in features or the ability for users to sign-up with any email and password combination, I've got it covered. Additionally, my proficiency in Firebase will guarantee efficient database management throughout your app.
Furthermore, my diverse skillset which includes PHP, Swift, JavaScript among others is a perfect match for this project. Not only will I deliver according to your specifications but also offer the potential to incorporate enhanced functionalities in the future. Let me realize your vision by creating a flutter app that's both technically sound and visually appealing. Looking forward to working together!