fix: sync sadhna calendar with local timezone

internal/repository/post_repo.go

@@ -243,18 +243,22 @@ func (r *PostRepo) PostedDates(ctx context.Context, userID string, since time.Ti
 	return out, rows.Err()
 }
 
-// PostCountsByDate returns, for each UTC calendar day on or after `since`,
-// how many posts the user created that day. Keys are "YYYY-MM-DD"; days
-// with no posts are absent (so a missing key reads as zero). The sādhana
-// vine uses this both for the "posted a quote today" discipline and to
-// annotate each day's fold with the number of quotes shared.
-func (r *PostRepo) PostCountsByDate(ctx context.Context, userID string, since time.Time) (map[string]int, error) {
+// PostCountsByDate returns, for each calendar day on or after `since`, how
+// many posts the user created that day — bucketed in the given IANA timezone
+// (`tz`) so the day boundary matches the user's local midnight. Keys are
+// "YYYY-MM-DD"; days with no posts are absent (so a missing key reads as
+// zero). The sādhana page uses this for the "posted a quote today" discipline
+// and to annotate each day's fold with the number of quotes shared.
+func (r *PostRepo) PostCountsByDate(ctx context.Context, userID string, since time.Time, tz string) (map[string]int, error) {
+	if tz == "" {
+		tz = "UTC"
+	}
 	rows, err := r.pg.Pool.Query(ctx, `
-		SELECT (created_at AT TIME ZONE 'UTC')::date AS d, count(*) AS n
+		SELECT (created_at AT TIME ZONE $3)::date AS d, count(*) AS n
 		FROM posts
 		WHERE user_id = $1 AND created_at >= $2
 		GROUP BY d`,
-		userID, since,
+		userID, since, tz,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("post counts by date: %w", err)