feat(files): document CLI uploads

Document Bearer-authenticated multipart uploads with curl and Wget2. Return 413 for oversized multipart bodies and report attachment size limits accurately.

internal/api/files.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"errors"
 	"net/http"
 
 	"github.com/lgcosta/notas-online/internal/store"
@@ -19,7 +20,12 @@ const maxUploadBody = store.MaxFileBytes + 64<<10
 func (s *Server) handleFileUpload(w http.ResponseWriter, r *http.Request) {
 	r.Body = http.MaxBytesReader(w, r.Body, maxUploadBody)
 	if err := r.ParseMultipartForm(8 << 20); err != nil {
-		writeError(w, http.StatusBadRequest, "multipart inválido ou excede limite: "+err.Error())
+		var maxErr *http.MaxBytesError
+		if errors.As(err, &maxErr) {
+			writeError(w, http.StatusRequestEntityTooLarge, "upload excede o limite de 64 MiB")
+		} else {
+			writeError(w, http.StatusBadRequest, "multipart inválido")
+		}
 		return
 	}
 	defer r.MultipartForm.RemoveAll()