Fix feature flag health check blocked by CORS

Use relative /health path through Vite proxy instead of absolute URL
to localhost:8000, matching the pattern used by all other API calls.

frontend/src/features/feature-flags/store.test.ts

@@ -7,10 +7,6 @@ vi.mock('../../shared/api/http', () => ({
   apiFetch: (...args: unknown[]) => mockApiFetch(...args),
 }))
 
-vi.mock('../settings/store', () => ({
-  useSettingsStore: () => ({ apiUrl: 'http://localhost:8000' }),
-}))
-
 describe('useFeatureFlagStore', () => {
   beforeEach(() => {
     setActivePinia(createPinia())

frontend/src/features/feature-flags/store.ts

@@ -1,7 +1,6 @@
 import { defineStore } from 'pinia'
 import { ref, computed } from 'vue'
 import { apiFetch } from '../../shared/api/http'
-import { useSettingsStore } from '../settings/store'
 
 type ConversionEngine = 'local' | 'remote'
 
@@ -44,9 +43,8 @@ export const useFeatureFlagStore = defineStore('feature-flags', () => {
   }
 
   async function load(): Promise<void> {
-    const settings = useSettingsStore()
     try {
-      const data = await apiFetch<HealthResponse>(`${settings.apiUrl}/health`)
+      const data = await apiFetch<HealthResponse>('/health')
       engine.value = data.engine
       loaded.value = true
       error.value = null

frontend/vite.config.js

@@ -9,6 +9,10 @@ export default defineConfig({
       '/api': {
         target: 'http://localhost:8000',
         changeOrigin: true
+      },
+      '/health': {
+        target: 'http://localhost:8000',
+        changeOrigin: true
       }
     }
   }