feat: Update App Section Content for Better Engagement

[akshay0611]

Summary: This PR updates the content of the app section to improve clarity, relevance, and engagement. The changes aim to better communicate the platform's strengths and value proposition.

Changes Made:

• Rewrote <p class="section-subtitle"> to emphasize the app as a fitness companion.
• Rewrote <h2 class="h2 section-title"> to focus on motivation and accessibility.
• Improved alt attributes for app store images to enhance accessibility and SEO.
• Ensured alignment with existing CSS styles and framework conventions.

Testing:

• Verified responsiveness across different screen sizes.
• Ensured proper rendering of the app section and its content.

Related Issue: Closes #11