feat: add feedback API client

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/api/feedback.ts

@@ -0,0 +1,21 @@
+import { apiClient } from './client'
+
+export interface FeedbackSubmission {
+  email: string
+  feedback_type: string
+  message: string
+}
+
+export interface FeedbackResponse {
+  success: boolean
+  message: string
+}
+
+export const feedbackApi = {
+  submit: async (data: FeedbackSubmission): Promise<FeedbackResponse> => {
+    const { data: response } = await apiClient.post('/feedback', data)
+    return response
+  },
+}
+
+export default feedbackApi