fix(mig 098): exempt orphan rules from §6.2 NULL-check (proceeding_type_id IS NULL)

Recovery during the prod outage uncovered a second mig 098 bug: §6.2
assertion '0 NULL submission_code on active+published rows' counted
the 77 orphan rules (proceeding_type_id IS NULL, cross-cutting
Wiedereinsetzung / Schriftsatznachreichung pattern) and rejected the
migration. Patch: gate the NULL count on `proceeding_type_id IS NOT
NULL` so orphans pass through. Migration already applied to prod via
manual recovery with the same patched assertion; this commit aligns
the in-repo file with the deployed state.

internal/db/migrations/098_submission_codes_prefix_and_rename.up.sql

@@ -240,13 +240,17 @@ BEGIN
             v_bad_shape;
     END IF;
 
-    -- 6.2 No NULL submission_code on active+published rows. The column
-    --     is nullable for legacy reasons, but every live row should
-    --     carry a code after the prefix step.
+    -- 6.2 No NULL submission_code on active+published rows that BELONG
+    --     to a proceeding. Orphan rows (`proceeding_type_id IS NULL`)
+    --     are cross-cutting rules without a fixed proceeding home
+    --     (Wiedereinsetzung, Schriftsatznachreichung, etc.) — they
+    --     legitimately carry NULL submission_code because there's no
+    --     proceeding to prefix with. Exempt them.
     SELECT count(*) INTO v_null_codes
       FROM paliad.deadline_rules
      WHERE is_active = true
        AND lifecycle_state = 'published'
+       AND proceeding_type_id IS NOT NULL
        AND submission_code IS NULL;
     IF v_null_codes <> 0 THEN
         RAISE EXCEPTION