fix: sync timezone fix

internal/service/sadhna_service.go

@@ -85,9 +85,16 @@ const fallbackTZ = "Asia/Kolkata"
 
 // resolveTZ returns the user's IANA timezone name + loaded location, falling
 // back to Asia/Kolkata (then UTC) so the day boundary is always defined.
+//
+// The users.timezone column defaults to 'UTC' (migration 0028), so a bare
+// "UTC" means the browser never reported a real zone — i.e. we don't actually
+// know the user's local time. Per product intent we treat that as unknown and
+// fall back to India time, rather than literally bucketing their day at UTC
+// midnight (which mismatches the browser-local calendar on the client). A
+// genuine UTC user re-reports their real zone on next load.
 func (s *SadhnaService) resolveTZ(ctx context.Context, userID string) (string, *time.Location) {
 	tz, _ := s.logs.UserTimezone(ctx, userID)
-	if tz == "" {
+	if tz == "" || tz == "UTC" {
 		tz = fallbackTZ
 	}
 	loc, err := time.LoadLocation(tz)