Schedules a one-shot Pebble wakeup for the configured notification
time, re-arming it on every launch and config change, and vibrates/
refreshes the report when it fires (foreground or fresh launch).
Also adds a `make watchapp` target that builds the watchapp via the
Pebble SDK and copies a versioned .pbw to dist/, matching `make
package`'s version resolution — deliberately not wired into CI, which
has no Pebble SDK installed.
ml