Move gear backfill logic from the route handler into
import_garmin_gear(data_dir, user_dir) in garmin_sync.py so it can be
called both from the API and from the CLI script.
scripts/backfill_garmin_gear.py finds all users with Garmin credentials
and runs the backfill for each, printing a per-user summary.
- garmin_sync_iter: sync gear registry from Garmin on every sync run and
resolve gear for each newly imported activity via get_activity_gear()
- POST /api/garmin/import-gear: one-time backfill that matches Garmin gear
activities to existing local activities by UTC timestamp (±60 s)
Matches the Strava sync table layout. Accumulates total_imported in
garmin_sync.json state on each sync run; admin API exposes last_sync_at
and total_imported from that file.
Davide Scaini