refactor(db): switch records layer to Prisma

- Replace hand-written node:sqlite queries with a Prisma client using
  the better-sqlite3 driver adapter
- Version the schema with migrations: baseline table, timestamp
  normalisation, and WAL journal mode
- Store timestamps with an explicit UTC offset so they stop being parsed
  as local time
- Show created/updated times on the edit page, formatted with dayjs
- Move the root redirect into next.config to avoid a prerender error
- Run migrations from the container entrypoint before starting the server

BREAKING CHANGE: DNSMASQ_ADMIN_DB_PATH is replaced by DATABASE_URL, which
must be a Prisma connection URL (file:./data/dnsmasq-admin.db). Existing
database files are migrated in place and need no conversion.

docker-entrypoint.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+# Apply any pending schema migrations before serving traffic.
+#
+# The database lives in a volume that outlives the container, so an image upgrade ships new
+# migrations without them having been applied yet. Running them here makes deploying a new
+# version a plain restart. `migrate deploy` is repeatable and never resets data.
+set -e
+
+# Reaches for the local binary rather than corepack/pnpm: this must succeed even when the
+# container has no outbound network.
+echo "applying database migrations…"
+node_modules/.bin/prisma migrate deploy
+
+exec "$@"