Update handlers accept an optional X-Base-Updated-At token and reject a stale overwrite with 409, returning the current server row. An absent token keeps the existing last-write-wins behaviour, so older clients are unaffected. packing_items gains an updated_at column (migration + stamped on every insert) so it can take part in conflict detection too.
Hourly reset now restores entire DB from baseline snapshot instead of
just deleting demo trips. This reverts ALL demo user changes including
modifications to shared admin trips. Admin credentials (password, API
keys) are preserved across resets. Admin can save new baseline via
Admin Panel button. Removed demoWriteBlock middleware.
DEMO_MODE=true enables: auto-seeded admin + demo user, 3 example trips
(Tokyo, Barcelona, Wien), hourly reset of demo user data, one-click
demo login, visible banner with feature info. Zero behavior change
when DEMO_MODE is not set.
Maurice