This site is static. The full-text index in
db/diary.db is SQLite FTS5 and is queried by the reader application in
the browser, so there is no server-side query endpoint here — and a search form
that silently ignored its query string would be worse than none.
Open the reader and use its search function. It queries the same 224-page corpus through the browser's own index.
curl … | grep.#page-N anchor per page.