Last year I started breaking down some loose documents into notes in a personal zettlekasten. The notes are Markdown files with a couple scripts, one to create new files under a short ID, and another search notes for text and insert matching files' titles and IDs as Markdown links. To bring the notes along with me when I'm away from my computer, I created a cacheable website that runs from my laptop, loads on my phone, then can be left behind while still giving offline access. The web server is written in Clojure, run with Babashka, and is about 130 lines long. The client-side JavaScript is about 100 lines and minifies to 1.9 kilobytes, gzips to less than 1 kB.
Despite its minimal size, the front-end has several features I've found helpful for navigating notes:
The repo is here. Feel free to fork it as a basis for your own custom zettelkasten.