Add Snaptium to the Electron note-taking tools section.

[jetyu]

What does this PR do?

Adds Snaptium to the Electron section.

Snaptium is an open-source, local-first Markdown note-taking and knowledge management application with AI-assisted writing, RAG-based Q&A, multi-device sync, and end-to-end encryption.

Checklist

• I have read the [contribution guidelines](contributing.md)
• The entry follows the correct format: - [icons] [Name](URL) - Description. \LICENSE Tech``
• The tool is not already on the list
• The tool is actively maintained (last commit within 12 months)
• Icons are accurate (checked platform support, sync, encryption)
• The link works and points to the official source
• For open-source tools: license (SPDX) and tech stack are included
• Added to the correct category