feat(store): establish Pinia store architecture and best practices (#39)

[isaaceliape]

Summary

This PR implements issue #39: Establish Pinia store architecture and best practices

Changes

✅ Documentation (2,200+ lines)

• docs/pinia-store-architecture.md - Complete store architecture guide with best practices
• docs/naming-conventions.md - Naming conventions for state, getters, actions, types
• docs/store-examples-migration.md - Practical examples and Vuex migration guide

✅ Code Implementation

• src/store/types.ts - TypeScript type definitions for store state
• src/store/utilities.ts - Factory functions for consistent store patterns
• src/store/app.ts - Updated with improved type imports
• README.md - Added store architecture section and documentation links

Key Improvements

• Clear Naming Conventions: camelCase state, get prefix for getters, verb prefixes for actions
• Module Separation Strategy: Defined for future growth and scalability
• Factory Functions: Setters, toggles, increments, array operations, persistence utilities
• Comprehensive Examples: Component integration, async operations, state persistence
• Migration Guide: Complete Vuex to Pinia migration with checklist
• Full Type Safety: TypeScript interfaces for all state and action types

Acceptance Criteria Met

✅ Pinia store architecture document created with best practices
✅ Store structure follows Vue 3 Composition API patterns
✅ Naming conventions established (getters, actions, state)
✅ Module separation strategy defined
✅ TypeScript types for store state created
✅ Store documentation added to codebase
✅ Code passes linting and builds successfully

How to Test

1. Review the documentation in docs/pinia-store-architecture.md
2. Check the store examples in docs/store-examples-migration.md
3. Review naming conventions in docs/naming-conventions.md
4. Run bun run lint - all checks pass
5. Run bun run build - production build succeeds

Checklist

• Tests pass locally (79 tests passing)
• Code follows project guidelines (ESLint: 0 errors)
• Documentation updated and comprehensive
• No breaking changes
• Store architecture ready for phase 2 migration

---

Closes #39