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/stores/authStore.ts

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+import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
+
+// User type - will be replaced with generated types later
+interface User {
+  id: string;
+  email: string;
+  full_name?: string;
+  is_active: boolean;
+  is_superuser: boolean;
+  organization_id?: string;
+}
+
+interface AuthState {
+  // State
+  user: User | null;
+  accessToken: string | null;
+  refreshToken: string | null;
+  isAuthenticated: boolean;
+
+  // Actions
+  setUser: (user: User) => void;
+  setTokens: (accessToken: string, refreshToken: string) => void;
+  setAuth: (user: User, accessToken: string, refreshToken: string) => void;
+  clearAuth: () => void;
+}
+
+export const useAuthStore = create<AuthState>()(
+  persist(
+    (set) => ({
+      // Initial state
+      user: null,
+      accessToken: null,
+      refreshToken: null,
+      isAuthenticated: false,
+
+      // Actions
+      setUser: (user) =>
+        set({
+          user,
+          isAuthenticated: true,
+        }),
+
+      setTokens: (accessToken, refreshToken) =>
+        set({
+          accessToken,
+          refreshToken,
+        }),
+
+      setAuth: (user, accessToken, refreshToken) =>
+        set({
+          user,
+          accessToken,
+          refreshToken,
+          isAuthenticated: true,
+        }),
+
+      clearAuth: () =>
+        set({
+          user: null,
+          accessToken: null,
+          refreshToken: null,
+          isAuthenticated: false,
+        }),
+    }),
+    {
+      name: 'auth-storage', // localStorage key
+      partialize: (state) => ({
+        // Only persist these fields
+        user: state.user,
+        accessToken: state.accessToken,
+        refreshToken: state.refreshToken,
+        isAuthenticated: state.isAuthenticated,
+      }),
+    }
+  )
+);

frontend/src/stores/index.ts

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+// Zustand stores
+// Examples: authStore, uiStore, etc.
+
+export { useAuthStore } from './authStore';