docs: add blog with first post on organizing code snippets

[antonreshetov]

Opens a /blog section and adds the first awareness post.

• New post /blog/how-to-organize-code-snippets targets "how do you organize code snippets" / "how to organize code snippets" (real GSC demand at ~position 9-10) and "best way to store code snippets".
• Value-first, evergreen system (one home, organize for retrieval, name + context, keep it close, own your data) with a copyable folder/tag structure and an FAQ for featured snippets.
• Links into the best-code-snippet-managers hub and massCode vs GitHub Gist; massCode mentioned naturally, not as a hard pitch.
• Adds a Blog nav entry and a /blog/ sidebar.