Previously, `CreateChat` inserted the `chats` row with the DB default
status (`waiting`), then updated it to `pending` in the same transaction
via `setChatPendingWithStore`. This wasted two extra queries per chat
creation (`GetChatByID` + `UpdateChatStatus`) and rewrote the same row
immediately after inserting it.
Now `CreateChat` passes the status directly to `InsertChat`, so the row
is written once in its final create-time state. The
`setChatPendingWithStore` helper is removed entirely. `InsertChat` now
requires an explicit `status` parameter at all callsites instead of
relying on a DB column default.
## Motivation
On an experimental branch we're trialing firing all chatd notifications
from plpgsql triggers. The old two-step insert made that awkward: in an
`AFTER INSERT` trigger, `NEW` only contained the insert-time row
(`waiting`), not the final committed state (`pending`). To emit the
correct event payload the trigger had to be deferred and re-read the row
from `chats` at commit time.
With this change, `NEW` already contains the correct row to publish — no
deferred trigger, no extra `SELECT`, simpler and cheaper trigger logic.
That said, this seems like a worthwhile change regardless of the trigger
experiment: writing the final row state once removes unnecessary DB work
on every chat creation and makes the create path easier to reason about.