feat(files): add folder download as zip

- Add zip folder API endpoint
- Add download button to folder rows
- Enforce max archive size limit
- Document endpoint in OpenAPI

lib/agent/agent.go

@@ -84,6 +84,7 @@ func (a *Agent) Serve() error {
 	mux.HandleFunc("/openapi.json", a.handleOpenAPI)
 	mux.HandleFunc("/api/v1/status", a.handleStatus)
 	mux.HandleFunc("/api/v1/files", a.handleFiles)
+	mux.HandleFunc("/api/v1/files/zip", a.handleZipFolder)
 	mux.HandleFunc("/api/v1/download", a.handleDownload)
 	mux.HandleFunc("/api/v1/upload", a.handleUpload)
 	mux.HandleFunc("/api/v1/screenshot", a.handleScreenshot)