feat(core): import progress & perf (#15197)

#### PR Dependency Tree


* **PR #15197** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added a new import pipeline with “plan then commit” batch handling for
Markdown, Notion HTML, Obsidian, and Bear backups.
* Enabled native import sessions with progress, cancellation, and
batch-by-batch committing (including assets, folders, icons, and tags).
  * Added web preflight limits for ZIP and multi-file imports.
* **Bug Fixes**
* Improved import error/warning reporting and continued processing when
some items fail.
* Strengthened snapshot-based file/directory picking to preserve paths.
* **Chores**
  * Updated project packaging/configuration for the new import workflow.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/apps/electron/src/shared/import.ts

@@ -0,0 +1,28 @@
+export type NativeImportFormat =
+  | 'markdownZip'
+  | 'notionZip'
+  | 'obsidian'
+  | 'bearZip';
+
+export type NativeImportBrowserSource =
+  | { kind: 'file'; file: File }
+  | { kind: 'directory'; files: File[] };
+
+export type CreateImportSessionFromSourceOptions = {
+  format: NativeImportFormat;
+  source: NativeImportBrowserSource;
+  batchLimits?: {
+    maxDocs?: number;
+    maxBlobs?: number;
+    maxBlobBytes?: number;
+  };
+};
+
+export type NativeImportSessionHandlers = {
+  createImportSession(
+    options: CreateImportSessionFromSourceOptions
+  ): Promise<string> | string;
+  nextImportBatch(sessionId: string): Promise<string | null> | string | null;
+  cancelImportSession(sessionId: string): Promise<void> | void;
+  disposeImportSession(sessionId: string): Promise<void> | void;
+};