fix(submissions): order catalog by sequence_order, not alphabetic submission_code

The Schriftsätze list rendered procedurally meaningless: Berufungsbegründung
ahead of Klageerhebung etc. because the ORDER BY was alphabetic by
submission_code within each proceeding. Add dr.sequence_order ASC as the
primary intra-proceeding sort; submission_code stays as the deterministic
tiebreaker for rules sharing a sequence_order.

deadline_rules.sequence_order is already populated for every published
filing rule (verified via paliad.deadline_rules_unified). Pure read-side
fix; no schema or data change.

internal/handlers/submissions.go

@@ -208,7 +208,7 @@ func loadSubmissionCatalog(ctx context.Context, projectProceedingTypeID *int) ([
 		    AND dr.submission_code IS NOT NULL
 		    AND dr.submission_code <> ''
 		    AND pt.is_active = true
-		  ORDER BY pt.code ASC, dr.submission_code ASC`)
+		  ORDER BY pt.code ASC, dr.sequence_order ASC, dr.submission_code ASC`)
 	if err != nil {
 		return nil, nil, err
 	}