Research: Redux Toolkit 2.x selected for state management

- Completed Redux vs Zustand vs Jotai comparison
- Redux Toolkit selected (9.2/10 score)
- Best for complex state (family structure, permissions)
- Best for offline sync (RTK Query, optimistic updates)
- Largest ecosystem (most resources, tutorials, examples)
- Best developer experience (time-travel debugging)
- 100% code sharing between React Native and React

Trade-offs:
- More boilerplate (clearer structure)
- Steeper learning curve (better patterns)
- Larger bundle 60KB vs 3KB (negligible impact)

Updated tech stack decisions and README

Next: Authentication system design (JWT with recovery phrases)

README.md

@@ -20,12 +20,16 @@ To record as many variables related to health as possible, store them in a secur
 ### Mobile (iOS + Android)
 - **Framework**: React Native 0.73+
 - **Language**: TypeScript
+- **State Management**: Redux Toolkit 2.x
+- **Data Fetching**: RTK Query 2.x
 - **Health Sensors**: react-native-health, react-native-google-fit
 - **Encryption**: react-native-quick-crypto
 
 ### Web
 - **Framework**: React 18+
 - **Language**: TypeScript
+- **State Management**: Redux Toolkit 2.x
+- **Data Fetching**: RTK Query 2.x
 - **Charts**: Recharts
 
 ### Deployment
@@ -71,9 +75,9 @@ Phase: Planning/Documentation
 - Git repository initialization
 - **Rust framework selection: Axum**
 - **Mobile/Web framework selection: React Native + React**
+- **State management selection: Redux Toolkit 2.x**
 
 ### Next Steps
-- State management research (Redux vs Zustand)
 - Authentication system design (JWT with recovery phrases)
 - Database schema design
 - Create proof-of-concept with Axum