feat: Expo scaffold + auth screens + core screens (#39-#46, #48)

stores/authStore.ts

@@ -0,0 +1,51 @@
+import { create } from 'zustand';
+import * as SecureStore from 'expo-secure-store';
+import { api } from '../services/api';
+
+interface AuthState {
+  token: string | null;
+  tenantSlug: string | null;
+  user: any | null;
+  isLoading: boolean;
+  login: (tenantSlug: string, username: string, password: string) => Promise<void>;
+  logout: () => Promise<void>;
+  hydrate: () => Promise<void>;
+}
+
+export const useAuthStore = create<AuthState>((set) => ({
+  token: null,
+  tenantSlug: null,
+  user: null,
+  isLoading: true,
+
+  hydrate: async () => {
+    try {
+      const token = await SecureStore.getItemAsync('auth_token');
+      const tenantSlug = await SecureStore.getItemAsync('tenant_slug');
+      if (token && tenantSlug) {
+        const res = await api.get('/api/v1/auth/me');
+        set({ token, tenantSlug, user: res.data, isLoading: false });
+      } else {
+        set({ isLoading: false });
+      }
+    } catch {
+      await SecureStore.deleteItemAsync('auth_token');
+      await SecureStore.deleteItemAsync('tenant_slug');
+      set({ token: null, tenantSlug: null, user: null, isLoading: false });
+    }
+  },
+
+  login: async (tenantSlug, username, password) => {
+    const res = await api.post('/api/v1/auth/login', { tenantSlug, username, password });
+    const { token, user } = res.data;
+    await SecureStore.setItemAsync('auth_token', token);
+    await SecureStore.setItemAsync('tenant_slug', tenantSlug);
+    set({ token, tenantSlug, user });
+  },
+
+  logout: async () => {
+    await SecureStore.deleteItemAsync('auth_token');
+    await SecureStore.deleteItemAsync('tenant_slug');
+    set({ token: null, tenantSlug: null, user: null });
+  },
+}));