ui: include frontmatter tags in tags sidebar section

[junereycasuga]

Summary

This PR makes frontmatter tags a first-class source for note tags, alongside inline #tags.

Previously, the sidebar/tag metadata pipeline only picked up inline hashtag syntax. Notes that already had tags in notes frontmatter, such as:

---
tags: [project, daily, area/work]
---

would not contribute those tags to the sidebar unless the same tags also appeared in the body.

Changes

• Include tags from frontmatter when extracting note tags.
• Support common frontmatter tag formats:
  • inline arrays: tags: [daily, work]
  • block lists:

tags:
  - daily
  - work

 - quoted tags and tags with a leading #
 - nested tags like project/compiler

• Keep inline #tag extraction behavior unchanged.
• Ignore non-tags frontmatter fields containing #, e.g. title: #ignored.
• Bump the note metadata cache version so existing notes are reparsed and old cached metadata does not hide pre-existing frontmatter tags.
• Keep desktop, renderer, MCP, and server tag extraction paths consistent.
• Add regression coverage for frontmatter tag extraction.

Validation

• npm run test:run --workspace @zennotes/app-core -- tags.test.ts
• npm run test:run --workspace @zennotes/desktop -- vault.test.ts
• go test ./internal/vault
• app-core and desktop node typechecks passed.