perf: full-stack performance and security hardening

Frontend performance:
- Debounce DataGrid search (150ms) and replace O(n) row wrapping with index array
- Replace QueryStore deep watcher with targeted field-level persistence snapshot
- Extract shared nodeConfig computed in TreeItem (eliminates 15x redundant getConfig calls)
- Clear tab result data on close to free memory
- Add LRU eviction for completion caches (50 entry cap)
- Replace savedSql version string join with numeric counter

Memory leak fixes:
- Store Tauri event unlisten handles and clean up on unmount
- Clean up DataGrid search timer on unmount

Backend security & resource management:
- Add 50MB request body size limit
- Reject file uploads >100MB and SQL files >200MB
- Clean up SSE channels after transfer/import completes
- Recover from poisoned mutex instead of panicking
- Delete temporary upload files after preview
- Validate SQL file paths to prevent directory traversal

src/components/grid/DataGrid.vue

@@ -219,6 +219,9 @@ const sortCol = ref<string | null>(null);
 const sortColIndex = ref<number | null>(null);
 const sortDir = ref<"asc" | "desc">("asc");
 const searchText = ref("");
+const deferredClientSearchText = ref("");
+let _searchTimer: ReturnType<typeof setTimeout> | undefined;
+
 const searchSuggestions = ref<string[]>([]);
 const suggestionIndex = ref(-1);
 const searchInputRef = ref<HTMLInputElement>();
@@ -279,9 +282,18 @@ function rowMatchesLocalColumnFilters(data: CellValue[]): boolean {
 }
 
 const localFilteredRows = computed(() => {
-  const rows = props.result.rows.map((row, sourceIndex) => ({ row, sourceIndex }));
-  if (!hasLocalColumnFilters.value) return rows;
-  return rows.filter(({ row, sourceIndex }) => rowMatchesLocalColumnFilters(rowDataWithChanges(row, sourceIndex)));
+  const rows = props.result.rows;
+  const indices: number[] = [];
+  if (!hasLocalColumnFilters.value) {
+    for (let i = 0; i < rows.length; i++) indices.push(i);
+    return indices;
+  }
+  for (let i = 0; i < rows.length; i++) {
+    if (rowMatchesLocalColumnFilters(rowDataWithChanges(rows[i], i))) {
+      indices.push(i);
+    }
+  }
+  return indices;
 });
 
 function buildLocalFilterOptions(columnIndex: number) {
@@ -838,6 +850,17 @@ const isFullPage = computed(() => props.result.rows.length >= pageSize.value);
 const isResultsContext = computed(() => props.context === "results");
 const canUseWhereSearch = computed(() => !!props.tableMeta && !!props.onExecuteSql && !isResultsContext.value);
 const clientSearchText = computed(() => (searchText.value.trim() ? searchText.value : ""));
+watch(clientSearchText, (value) => {
+  clearTimeout(_searchTimer);
+  const q = value.trim().toLowerCase();
+  if (!q) {
+    deferredClientSearchText.value = "";
+    return;
+  }
+  _searchTimer = setTimeout(() => {
+    deferredClientSearchText.value = q;
+  }, 150);
+});
 
 function currentWhereInput(): string | undefined {
   return whereFilterInput.value.trim() || undefined;
@@ -936,15 +959,16 @@ function onToolbarRollback() {
 }
 
 const sortedRows = computed(() => {
-  let rows = localFilteredRows.value;
-  if (clientSearchText.value) {
-    const q = clientSearchText.value.toLowerCase();
-    rows = rows.filter(({ row, sourceIndex }) => {
-      const data = rowDataWithChanges(row, sourceIndex);
+  let indices = localFilteredRows.value;
+  const q = deferredClientSearchText.value;
+  if (q) {
+    const rows = props.result.rows;
+    indices = indices.filter((sourceIndex) => {
+      const data = rowDataWithChanges(rows[sourceIndex], sourceIndex);
       return data.some((cell) => cell !== null && String(cell).toLowerCase().includes(q));
     });
   }
-  return rows;
+  return indices;
 });
 
 function rowDataWithChanges(row: CellValue[], sourceIndex: number): CellValue[] {
@@ -965,7 +989,9 @@ interface RowItem {
 
 const displayItems = computed<RowItem[]>(() => {
   const cols = props.result.columns;
-  const items: RowItem[] = sortedRows.value.map(({ row, sourceIndex }) => {
+  const rows = props.result.rows;
+  const items: RowItem[] = sortedRows.value.map((sourceIndex) => {
+    const row = rows[sourceIndex];
     const dirty = dirtyRows.value.get(sourceIndex);
     const data = rowDataWithChanges(row, sourceIndex);
     const isDirtyCol = row.map((_, colIdx) => dirty?.has(colIdx) ?? false);
@@ -989,7 +1015,7 @@ const displayItems = computed<RowItem[]>(() => {
 });
 const hasVisibleRows = computed(() => displayItems.value.length > 0);
 const hasActiveFilter = computed(
-  () => !!clientSearchText.value || rowStatusFilter.value !== "all" || hasLocalColumnFilters.value,
+  () => !!deferredClientSearchText.value || rowStatusFilter.value !== "all" || hasLocalColumnFilters.value,
 );
 const totalFilterableRowCount = computed(() => props.result.rows.length + newRows.value.length);
 const emptyTitle = computed(() => (hasActiveFilter.value ? t("grid.noFilteredRows") : t("grid.noRows")));
@@ -2130,6 +2156,7 @@ onUnmounted(() => {
   if (cancelScrollRestoreFrame) cancelAnimationFrame(cancelScrollRestoreFrame);
   onDdlResizeEnd();
   finishCellSelection();
+  clearTimeout(_searchTimer);
 });
 
 const SQL_KEYWORDS =

src/components/sidebar/TreeItem.vue

@@ -1112,52 +1112,51 @@ function openFieldLineage() {
 }
 
 const canExpand = !leafTypes.has(props.node.type);
+const nodeConfig = computed(() =>
+  props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined,
+);
 const canPin = computed(() => pinnableTypes.has(props.node.type));
 const canOpenSqlFileExecution = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
-  return !!config && !SQL_FILE_UNSUPPORTED_TYPES.has(config.db_type);
+  return !!nodeConfig.value && !SQL_FILE_UNSUPPORTED_TYPES.has(nodeConfig.value.db_type);
 });
 const canOpenDiagram = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
-  return !!props.node.database && !!config && DIAGRAM_SUPPORTED_TYPES.has(config.db_type);
+  return !!props.node.database && !!nodeConfig.value && DIAGRAM_SUPPORTED_TYPES.has(nodeConfig.value.db_type);
 });
 const canOpenDatabaseSearch = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
-  return !!props.node.database && !!config && DATABASE_SEARCH_SUPPORTED_TYPES.has(config.db_type);
+  return !!props.node.database && !!nodeConfig.value && DATABASE_SEARCH_SUPPORTED_TYPES.has(nodeConfig.value.db_type);
 });
 const canOpenObjectBrowser = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
   return (
     (props.node.type === "database" || props.node.type === "schema" || props.node.type === "object-browser") &&
-    !!config &&
-    config.db_type !== "redis" &&
-    config.db_type !== "mongodb" &&
-    config.db_type !== "elasticsearch"
+    !!nodeConfig.value &&
+    nodeConfig.value.db_type !== "redis" &&
+    nodeConfig.value.db_type !== "mongodb" &&
+    nodeConfig.value.db_type !== "elasticsearch"
   );
 });
 const canOpenTableImport = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
-  return (
-    props.node.type === "table" && !!props.node.database && !!config && TABLE_IMPORT_SUPPORTED_TYPES.has(config.db_type)
-  );
-});
-const canOpenStructureEditor = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
   return (
     props.node.type === "table" &&
     !!props.node.database &&
-    !!config &&
-    TABLE_STRUCTURE_SUPPORTED_TYPES.has(config.db_type)
+    !!nodeConfig.value &&
+    TABLE_IMPORT_SUPPORTED_TYPES.has(nodeConfig.value.db_type)
+  );
+});
+const canOpenStructureEditor = computed(() => {
+  return (
+    props.node.type === "table" &&
+    !!props.node.database &&
+    !!nodeConfig.value &&
+    TABLE_STRUCTURE_SUPPORTED_TYPES.has(nodeConfig.value.db_type)
   );
 });
 const canOpenFieldLineage = computed(() => {
-  const config = props.node.connectionId ? connectionStore.getConfig(props.node.connectionId) : undefined;
   return (
     props.node.type === "column" &&
     !!props.node.database &&
     !!props.node.tableName &&
-    !!config &&
-    FIELD_LINEAGE_SUPPORTED_TYPES.has(config.db_type)
+    !!nodeConfig.value &&
+    FIELD_LINEAGE_SUPPORTED_TYPES.has(nodeConfig.value.db_type)
   );
 });
 const isPinned = computed(() => props.node.pinned || connectionStore.isTreeNodePinned(props.node.id));