Convert backend from submodule to regular directory

Remove submodule tracking; backend is now a plain directory in the repo.
Also update deploy workflow: remove --recurse-submodules.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/db/stops.go

@@ -0,0 +1,60 @@
+package db
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/jacek/pamietnik/backend/internal/domain"
+)
+
+type StopStore struct {
+	pool *pgxpool.Pool
+}
+
+func NewStopStore(pool *pgxpool.Pool) *StopStore {
+	return &StopStore{pool: pool}
+}
+
+func (s *StopStore) ListByDate(ctx context.Context, userID, date string) ([]domain.Stop, error) {
+	rows, err := s.pool.Query(ctx, `
+		SELECT st.stop_id, st.device_id, st.trip_id,
+		       st.start_ts, st.end_ts,
+		       st.center_lat, st.center_lon, st.duration_s,
+		       COALESCE(st.place_label, ''),
+		       st.place_details
+		FROM stops st
+		JOIN devices d ON d.device_id = st.device_id
+		WHERE d.user_id = $1
+		  AND DATE(st.start_ts AT TIME ZONE 'UTC') = $2::date
+		ORDER BY st.start_ts`,
+		userID, date,
+	)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	return pgx.CollectRows(rows, func(row pgx.CollectableRow) (domain.Stop, error) {
+		var st domain.Stop
+		err := row.Scan(
+			&st.StopID, &st.DeviceID, &st.TripID,
+			&st.StartTS, &st.EndTS,
+			&st.CenterLat, &st.CenterLon, &st.DurationS,
+			&st.PlaceLabel, &st.PlaceDetails,
+		)
+		return st, err
+	})
+}
+
+func (s *StopStore) Insert(ctx context.Context, st domain.Stop) error {
+	_, err := s.pool.Exec(ctx, `
+		INSERT INTO stops (stop_id, device_id, trip_id, start_ts, end_ts,
+		                   center_lat, center_lon, duration_s, place_label, place_details)
+		VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10)
+		ON CONFLICT (stop_id) DO NOTHING`,
+		st.StopID, st.DeviceID, st.TripID, st.StartTS, st.EndTS,
+		st.CenterLat, st.CenterLon, st.DurationS, st.PlaceLabel, st.PlaceDetails,
+	)
+	return err
+}