feat: export entire database as SQL file

Add a new "Export Database" feature accessible from the sidebar
right-click menu on database/schema nodes. Generates a .sql file
containing CREATE TABLE DDL, batched INSERT statements, and
view/procedure/function source code.

Backend (database_export.rs):
- Stream-writes SQL to file with configurable batch size
- Supports all SQL database types via existing DDL/INSERT generators
- Progress events with cancellation support
- Graceful error handling (continues on per-table failures)

Frontend (DatabaseExportDialog.vue):
- Connection/database/schema selector
- Checkboxes: structure, data, objects
- Real-time progress with current table and row count
- Cancel button

Wired up through Tauri commands, Web SSE routes, and API layer.

src/lib/api.ts

@@ -98,6 +98,10 @@ export const previewTableImportFile = forward("previewTableImportFile");
 export const importTableFile = forward("importTableFile");
 export const cancelTableImport = forward("cancelTableImport");
 
+// Database Export
+export const exportDatabaseSql = forward("exportDatabaseSql");
+export const cancelDatabaseExport = forward("cancelDatabaseExport");
+
 // Redis
 export const redisListDatabases = forward("redisListDatabases");
 export const redisScanKeys = forward("redisScanKeys");
@@ -172,4 +176,6 @@ export type {
   TableImportRequest,
   TableImportSummary,
   TableImportProgress,
+  DatabaseExportRequest,
+  ExportProgress,
 } from "./tauri";

src/lib/http.ts

@@ -38,6 +38,8 @@ import type {
   TableImportRequest,
   TableImportSummary,
   TableImportProgress,
+  DatabaseExportRequest,
+  ExportProgress,
 } from "./tauri";
 
 // ---------------------------------------------------------------------------
@@ -497,6 +499,44 @@ export async function cancelTableImport(importId: string): Promise<boolean> {
   return post("/api/import/cancel", { importId });
 }
 
+// ---------------------------------------------------------------------------
+// Database Export
+// ---------------------------------------------------------------------------
+
+export async function exportDatabaseSql(
+  request: DatabaseExportRequest,
+  onProgress: (progress: ExportProgress) => void,
+): Promise<void> {
+  // 1. POST to start the export
+  const res = await fetch("/api/export/database", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ request }),
+  });
+  if (!res.ok) throw new Error(await res.text());
+
+  // 2. SSE to listen for progress
+  return new Promise((resolve, reject) => {
+    const es = new EventSource(`/api/export/database/progress/${request.exportId}`);
+    es.onmessage = (e) => {
+      const progress: ExportProgress = JSON.parse(e.data);
+      onProgress(progress);
+      if (progress.status === "Done" || progress.status === "Error" || progress.status === "Cancelled") {
+        es.close();
+        resolve();
+      }
+    };
+    es.onerror = () => {
+      es.close();
+      reject(new Error("Export SSE connection failed"));
+    };
+  });
+}
+
+export async function cancelDatabaseExport(exportId: string): Promise<void> {
+  await post("/api/export/database/cancel", { exportId });
+}
+
 // ---------------------------------------------------------------------------
 // Redis
 // ---------------------------------------------------------------------------

src/lib/tauri.ts

@@ -744,3 +744,51 @@ export async function importTableFile(
 export async function cancelTableImport(importId: string): Promise<boolean> {
   return invoke("cancel_table_import", { importId });
 }
+
+// --- Database Export ---
+export interface DatabaseExportRequest {
+  exportId: string;
+  connectionId: string;
+  database: string;
+  schema: string;
+  filePath: string;
+  includeStructure: boolean;
+  includeData: boolean;
+  includeObjects: boolean;
+  batchSize: number;
+}
+
+export interface ExportProgress {
+  exportId: string;
+  currentObject: string;
+  objectIndex: number;
+  totalObjects: number;
+  rowsExported: number;
+  totalRows: number | null;
+  status: "Running" | "Done" | "Error" | "Cancelled";
+  error: string | null;
+}
+
+export async function exportDatabaseSql(
+  request: DatabaseExportRequest,
+  onProgress: (progress: ExportProgress) => void,
+): Promise<void> {
+  const unlisten: UnlistenFn = await listen<ExportProgress>("database-export-progress", (event) => {
+    if (event.payload.exportId === request.exportId) {
+      onProgress(event.payload);
+      if (event.payload.status === "Done" || event.payload.status === "Error" || event.payload.status === "Cancelled") {
+        unlisten();
+      }
+    }
+  });
+  try {
+    await invoke("export_database_sql", { request });
+  } catch (e) {
+    unlisten();
+    throw e;
+  }
+}
+
+export async function cancelDatabaseExport(exportId: string): Promise<void> {
+  await invoke("cancel_database_export", { exportId });
+}