feat(evidence): add upload types and API client for frontend

- FileUploadResponse and PendingUpload types in types/upload.ts
- uploadsApi with upload(), getUrl(), list(), remove() methods
- Exported from types/index.ts and api/index.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/api/index.ts

@@ -29,3 +29,4 @@ export { flowProposalsApi } from './flowProposals'
 export { flowpilotAnalyticsApi } from './flowpilotAnalytics'
 export { notificationsApi } from './notifications'
 export { publicTemplatesApi } from './publicTemplates'
+export { uploadsApi, default as uploadsApiDefault } from './uploads'

frontend/src/api/uploads.ts

@@ -0,0 +1,32 @@
+import apiClient from './client'
+import type { FileUploadResponse } from '@/types/upload'
+
+export const uploadsApi = {
+  async upload(file: File, sessionId?: string): Promise<FileUploadResponse> {
+    const formData = new FormData()
+    formData.append('file', file)
+    if (sessionId) formData.append('session_id', sessionId)
+    const response = await apiClient.post<FileUploadResponse>('/uploads', formData, {
+      headers: { 'Content-Type': 'multipart/form-data' },
+    })
+    return response.data
+  },
+
+  async getUrl(id: string): Promise<string> {
+    const response = await apiClient.get<{ url: string }>(`/uploads/${id}/url`)
+    return response.data.url
+  },
+
+  async list(sessionId: string): Promise<FileUploadResponse[]> {
+    const response = await apiClient.get<FileUploadResponse[]>('/uploads', {
+      params: { session_id: sessionId },
+    })
+    return response.data
+  },
+
+  async remove(id: string): Promise<void> {
+    await apiClient.delete(`/uploads/${id}`)
+  },
+}
+
+export default uploadsApi

frontend/src/types/index.ts

@@ -15,6 +15,7 @@ export type { AssistantChat, AssistantChatMessage, ChatListItem, ChatMessageResp
 export * from './ai-session'
 export * from './flow-proposal'
 export * from './flowpilot-analytics'
+export * from './upload'
 
 // API response wrapper types
 export interface PaginatedResponse<T> {

frontend/src/types/upload.ts

@@ -0,0 +1,17 @@
+export interface FileUploadResponse {
+  id: string
+  filename: string
+  content_type: string
+  size_bytes: number
+  url: string
+  created_at: string
+}
+
+export interface PendingUpload {
+  id: string
+  file: File
+  preview: string
+  status: 'uploading' | 'done' | 'error'
+  result?: FileUploadResponse
+  error?: string
+}