feat(export): move csv and xlsx generation to Rust backend

src-tauri/src/commands/csv_export.rs

@@ -0,0 +1,17 @@
+use dbx_core::csv_export::format_csv;
+use serde::Deserialize;
+use serde_json::Value;
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct QueryResultCsvExportRequest {
+    pub file_path: String,
+    pub columns: Vec<String>,
+    pub rows: Vec<Vec<Value>>,
+}
+
+#[tauri::command]
+pub fn export_query_result_csv(request: QueryResultCsvExportRequest) -> Result<(), String> {
+    let csv = format_csv(&request.columns, &request.rows);
+    std::fs::write(&request.file_path, format!("\u{FEFF}{csv}")).map_err(|err| err.to_string())
+}