feat(core): support Notion markdown zip imports (#14910)

## What changed
- Markdown zip imports now resolve local `.md` links like `./test/2.md`
into AFFiNE linked-page references when the target document exists in
the same archive.
- Added Notion Markdown `.zip` import support in the desktop import
dialog, including nested zip traversal, Notion title extraction,
hash-stripped folder names, attachments, and folder hierarchy
integration.
- Added i18n entries and adapter coverage for standard Markdown zip
links and Notion Markdown zip imports.

## Why
Markdown and Notion exports often contain links between notes using
relative `.md` paths. Keeping those as plain URLs makes imported
workspaces harder to navigate, so the importer now preassigns document
ids and rewrites resolvable archive-local markdown links into linked
pages.

## Notes
The markdown zip folder hierarchy implementation now comes from latest
`origin/canary`, so this PR only layers relative-link resolution and
Notion Markdown zip support on top of that upstream behavior.

## Validation
- `yarn vitest --run
blocksuite/affine/all/src/__tests__/adapters/markdown.unit.spec.ts`
- `yarn tsc -b blocksuite/affine/all/tsconfig.json --verbose`
- `git diff --check`

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

* **New Features**
* Added support for importing Notion Markdown exports in `.zip` format,
including subpages, attachments, and nested folders.
* Internal links inside imported Markdown now resolve correctly between
pages, preserving link text when available.
* The import dialog now includes a dedicated “Notion (Markdown, .zip)”
option.

* **Bug Fixes**
* Improved filename handling so non-Latin characters in ZIP imports are
preserved correctly.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>
Co-authored-by: DarkSky <darksky2048@gmail.com>

packages/frontend/i18n/src/i18n.gen.ts

@@ -2506,6 +2506,14 @@ export function useAFFiNEI18N(): {
       * `Import your Notion data. Supported import formats: HTML with subpages.`
       */
     ["com.affine.import.notion.tooltip"](): string;
+    /**
+      * `Notion (Markdown, .zip)`
+      */
+    ["com.affine.import.notion-markdown"](): string;
+    /**
+      * `Import a Notion Markdown export zip with subpages and attachments.`
+      */
+    ["com.affine.import.notion-markdown.tooltip"](): string;
     /**
       * `Obsidian Vault (Experimental)`
       */

packages/frontend/i18n/src/resources/en.json

@@ -625,6 +625,8 @@
   "com.affine.import.modal.tip": "If you'd like to request support for additional file types, feel free to let us know on",
   "com.affine.import.notion": "Notion (Experimental)",
   "com.affine.import.notion.tooltip": "Import your Notion data. Supported import formats: HTML with subpages.",
+  "com.affine.import.notion-markdown": "Notion (Markdown, .zip)",
+  "com.affine.import.notion-markdown.tooltip": "Import a Notion Markdown export zip with subpages and attachments.",
   "com.affine.import.obsidian": "Obsidian Vault (Experimental)",
   "com.affine.import.obsidian.tooltip": "Import an Obsidian vault. Select a folder to import all notes, images, and assets with wikilinks resolved.",
   "com.affine.import.snapshot": "Snapshot",