Add CSV file upload and auto-delimiter detection for pilot import

Allows uploading a CSV file directly instead of only pasting text, and
auto-detects comma vs semicolon separators to support more locales.

pilots.go

@@ -164,6 +164,18 @@ func handleDeletePilot(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusNoContent)
 }
 
+// detectSeparator counts commas vs semicolons in the first line to pick the delimiter.
+func detectSeparator(data []byte) rune {
+	sample := string(data)
+	if idx := strings.IndexByte(sample, '\n'); idx > 0 {
+		sample = sample[:idx]
+	}
+	if strings.Count(sample, ";") > strings.Count(sample, ",") {
+		return ';'
+	}
+	return ','
+}
+
 func handleImportPilots(w http.ResponseWriter, r *http.Request) {
 	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
 	if err != nil {
@@ -174,13 +186,34 @@ func handleImportPilots(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusForbidden, "forbidden")
 		return
 	}
-	// Cap the upload to keep memory bounded.
-	body, err := io.ReadAll(io.LimitReader(r.Body, 2*1024*1024))
-	if err != nil {
-		writeError(w, http.StatusBadRequest, "read_error")
-		return
+
+	var body []byte
+	if strings.HasPrefix(r.Header.Get("Content-Type"), "multipart/form-data") {
+		if err := r.ParseMultipartForm(2 * 1024 * 1024); err != nil {
+			writeError(w, http.StatusBadRequest, "read_error")
+			return
+		}
+		f, _, err := r.FormFile("file")
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "missing_file")
+			return
+		}
+		defer f.Close()
+		body, err = io.ReadAll(io.LimitReader(f, 2*1024*1024))
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "read_error")
+			return
+		}
+	} else {
+		body, err = io.ReadAll(io.LimitReader(r.Body, 2*1024*1024))
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "read_error")
+			return
+		}
 	}
+
 	reader := csv.NewReader(strings.NewReader(string(body)))
+	reader.Comma = detectSeparator(body)
 	reader.FieldsPerRecord = -1
 	records, err := reader.ReadAll()
 	if err != nil {