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.

lib/datetime.ts

@@ -0,0 +1,21 @@
+import dayjs from "dayjs"
+
+/** Single format used everywhere a timestamp is rendered, so the UI stays consistent. */
+const DISPLAY_FORMAT = "YYYY-MM-DD HH:mm:ss"
+
+/**
+ * Format a stored timestamp for display.
+ *
+ * Every timestamp carries an explicit `+00:00` offset (see prisma/migrations/0002), so dayjs
+ * always resolves the correct instant; it then renders it in the viewer's local zone. Before
+ * that migration the values looked like `2026-10-09 08:55:10`, which JavaScript parses as
+ * *local* time even though SQLite stored it UTC — an eight-hour error on a UTC+8 machine.
+ *
+ * Timestamps travel through the app as ISO strings (see lib/db.ts), so this helper takes a
+ * string rather than a `Date`.
+ */
+export function formatDateTime(value: string | null | undefined): string {
+  if (!value) return "—"
+  const parsed = dayjs(value)
+  return parsed.isValid() ? parsed.format(DISPLAY_FORMAT) : value
+}