[sdairs]

Adds applications/habit-tracker: a Next.js 16 habit tracker (App Router, Server Components, Server Actions, Click UI) using Drizzle ORM with node-postgres on ClickHouse Managed Postgres, provisioned with clickhousectl.

Database lesson: one check-in per habit per day. check_ins has a (habit_id, day) primary key. The checkbox sends its desired state rather than a toggle, and checking a day is a single INSERT … SELECT … ON CONFLICT DO NOTHING, so double clicks, retries and concurrent requests leave one row. Streaks are computed in SQL with a gaps-and-islands window query.

Included: the app, src/db.ts with verify-full TLS from the service CA (it refuses a remote host without a CA), drizzle-kit migrations, SQL for roles, grants, seed and cleanup, unit and integration tests, a README with every clickhousectl and psql step, a CI workflow (install, typecheck and unit tests, build), and one line in the root README.

Verified against ClickHouse Managed Postgres 18.6:

• 8 unit and 8 integration tests pass as the app role. These cover 20 concurrent check-ins leaving exactly one row, a raw duplicate failing with 23505, idempotent unchecking, streaks across gaps, ownership and archive checks, app-role DDL failing with 42501, and pg_stat_ssl reporting TLS.
• The README's schema steps ran twice from scratch, the cleanup block ran as written, and the "Try it" steps were checked in the UI.

Walkthrough article (production URL): https://clickhouse.com/resources/engineering/build-habit-tracker-nextjs-drizzle-postgres

🤖 Generated with Claude Code