Add foundational API client, UI components, and state management setup

- Created `generate-api-client.sh` for OpenAPI-based TypeScript client generation.
- Added `src/lib/api` with Axios-based API client, error handling utilities, and placeholder for generated types.
- Implemented Zustand-based `authStore` for user authentication and token management.
- Integrated reusable UI components (e.g., `Dialog`, `Select`, `Textarea`, `Sheet`, `Separator`, `Checkbox`) using Radix UI and utility functions.
- Established groundwork for client-server integration, state management, and modular UI development.

frontend/src/lib/api/generated/index.ts

@@ -0,0 +1,8 @@
+// This file will be auto-generated by running: npm run generate:api
+// Make sure the backend is running before generating the API client
+//
+// To generate: npm run generate:api
+//
+// This placeholder prevents import errors before generation
+
+export {}