refactor: reorganize features/shared directory for better maintainability (#730)

* refactor: reorganize features/shared directory structure

- Created organized subdirectories for better code organization:
  - api/ - API clients and HTTP utilities (renamed apiWithEtag.ts to apiClient.ts)
  - config/ - Configuration files (queryClient, queryPatterns)
  - types/ - Shared type definitions (errors)
  - utils/ - Pure utility functions (optimistic, clipboard)
  - hooks/ - Shared React hooks (already existed)

- Updated all import paths across the codebase (~40+ files)
- Updated all AI documentation in PRPs/ai_docs/ to reflect new structure
- All tests passing, build successful, no functional changes

This improves maintainability and follows vertical slice architecture patterns.

Co-Authored-By: Claude <noreply@anthropic.com>

* fix: address PR review comments and code improvements

- Update imports to use @/features alias path for optimistic utils
- Fix optimistic upload item replacement by matching on source_id instead of id
- Clean up test suite naming and remove meta-terms from comments
- Only set Content-Type header on requests with body
- Add explicit TypeScript typing to useProjectFeatures hook
- Complete Phase 4 improvements with proper query typing

* fix: address additional PR review feedback

- Clear feature queries when deleting project to prevent cache memory leaks
- Update KnowledgeCard comments to follow documentation guidelines
- Add explanatory comment for accessibility pattern in KnowledgeCard

---------

Co-authored-by: Claude <noreply@anthropic.com>

PRPs/ai_docs/ARCHITECTURE.md

@@ -88,8 +88,8 @@ Pattern: `{METHOD} /api/{resource}/{id?}/{sub-resource?}`
 
 ### Data Fetching
 **Core**: TanStack Query v5
-**Configuration**: `archon-ui-main/src/features/shared/queryClient.ts`
-**Patterns**: `archon-ui-main/src/features/shared/queryPatterns.ts`
+**Configuration**: `archon-ui-main/src/features/shared/config/queryClient.ts`
+**Patterns**: `archon-ui-main/src/features/shared/config/queryPatterns.ts`
 
 ### State Management
 - **Server State**: TanStack Query
@@ -139,7 +139,7 @@ TanStack Query is the single source of truth. No separate state management neede
 No translation layers. Database values (e.g., `"todo"`, `"doing"`) used directly in UI.
 
 ### Browser-Native Caching
-ETags handled by browser, not JavaScript. See `archon-ui-main/src/features/shared/apiWithEtag.ts`.
+ETags handled by browser, not JavaScript. See `archon-ui-main/src/features/shared/api/apiClient.ts`.
 
 ## Deployment