feat(db): gated training/demo database reset CLI

A site is sometimes run live to train operators/admins; afterwards the demo
data must go without an obvious self-serve button (the operator must not be
able to wipe history). Adds packages/db/scripts/reset-db.mjs, exposed as
`pnpm db:reset` (dev) and run via `docker exec ... node
node_modules/@parking/db/scripts/reset-db.mjs` on the booth (no pnpm there).

Category flags (combinable): --financial (ledger + telemetry + snapshots +
subscription instances + blocklist; keeps users/devices/config/tariffs/plans),
--config, --users, --all. Shifts/cash/payments live as event types inside the
hash-chained ledger_events, so --financial truncates the whole signed ledger
back to empty (re-seed starts a new chain under the SAME EVENT_SIGNING_KEY —
keys untouched).

Two safety gates: RESET_ALLOWED=1 env (a real booth never sets it) + typed
DB-filename confirmation (--yes skips for CI). Single transaction + VACUUM.

Verified on throwaway dev-DB copies: both gates refuse correctly; each flag
wipes/keeps the right tables; the real dev DB is never touched.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

packages/db/package.json

@@ -26,7 +26,8 @@
     "lint": "tsc --noEmit",
     "db:generate": "drizzle-kit generate",
     "db:migrate": "DATABASE_URL=\"${DATABASE_URL:-../../apps/server/parking.sqlite}\" drizzle-kit migrate",
-    "db:migrate:runtime": "node scripts/migrate-runtime.mjs"
+    "db:migrate:runtime": "node scripts/migrate-runtime.mjs",
+    "db:reset": "DATABASE_URL=\"${DATABASE_URL:-../../apps/server/parking.sqlite}\" node scripts/reset-db.mjs"
   },
   "dependencies": {
     "@parking/shared": "workspace:*",