docs: add architecture and application flow diagrams to README

Description

Problem

The README explains the project's feature-based architecture and folder structure, but it lacks visual diagrams illustrating how the application's modules interact. New contributors must infer the relationships between pages, components, feature modules, state management, services, and API layers.

Proposed Solution

Add an Architecture section to the README containing:

• High-level application architecture diagram
• Request flow diagram (UI → Feature → Store → Service → API)
• Feature module organization diagram
• State management flow
• Brief explanation accompanying each diagram

Benefits

• Improves onboarding for first-time contributors.
• Makes the feature-based architecture easier to understand.
• Reduces time spent exploring the codebase.
• Serves as a quick reference for future contributors.

Additional note

Hello mentor! I am GSSOC'26 contributor and if this issue aligns with the project requirements,kindly assign this to me.