v0.1: Review & import flowershow notes/ candidates

[rufuspollock]

Part of the v0.1 epic (#46).

Review markdown/PKM-general (non-product) candidates in flowershow/content/flowershow-app/notes/ and import keepers into kb/ (or why/essays where they fit):

• digital-garden.md
• why-the-new-wave-in-pkm-roam-obsidian-etc.md
• obsidian-database-research.md
• markdown-based-landing-page.md
• alternatives.md
• obsidian.md

Leave product-specific ones where they are. Also consider blog posts best-blogging-platforms-for-obsidian-users.md / obsidian-publish-alternatives.md (probably stay with the product site — decide).