add a selectable output format to setup_logging: text (default, human,
local time) stays unchanged; output="json" emits one-JSON-object-per-line
(JSON Lines) for the Grafana/Loki path. json fields are time (UTC ISO-8601
with Z), level, module, message, plus any extra={...} keys surfaced as
top-level fields and a rendered exc_info traceback on error records. both
file and console use the chosen format; the live-file name is unchanged so
the Promtail glob and tail command don't break across text/json. an unknown
output falls back to text and warns, never crashes. stdlib json only, zero
new deps. minor bump to v0.2.0.
Signed-off-by: disqualifier <dev@disqualifier.me>
