Refactored all stores to follow consistent patterns and best practices while keeping MobX:

New Infrastructure:
- Created base-store.ts with StandardState base class and factory functions
- Added store-utils.ts with RequestDeduplicator, StoreError, and OptimisticUpdate helpers
- Added config.ts for MobX configuration and strict mode
- Created comprehensive README.md with architecture guide and examples

Server State Stores (API data):
- attachment.ts: Added request deduplication, error handling, computed properties, delete/clear methods
- workspace.ts: Added Theme type validation, computed memoization, improved initialization
- memo.ts: Enhanced with optimistic updates, request deduplication, structured errors
- user.ts: Fixed temporal coupling, added computed memoization, request deduplication

Client State Stores (UI state):
- view.ts: Added helper methods (toggleSortOrder, setLayout, resetToDefaults), input validation
- memoFilter.ts: Added utility methods (hasFilter, clearAllFilters, removeFiltersByFactor)

Improvements:
- Request deduplication prevents duplicate API calls (all server stores)
- Computed property memoization improves performance
- Structured error handling with error codes
- Optimistic updates for better UX (memo updates)
- Comprehensive JSDoc documentation
- Type-safe APIs with proper exports
- Clear separation between server and client state

All stores now follow consistent patterns for better maintainability and easier onboarding.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>