fix(litigationplanner): mig 134 set_config('paliad.audit_reason') (HOTFIX 2, t-paliad-300, m/paliad#131)

Mig 134's step 4 UPDATEs paliad.deadline_rules to reassign 16 rules
to the unified upc.apl.unified proceeding_type. The mig-079 audit
trigger requires set_config('paliad.audit_reason', …, true) before
any mutation — mig 134 missed it, causing the migration runner to
abort with P0001 "audit reason required for UPDATE" on every boot
after #130 landed.

Adds the canonical set_config call at the top of both up + down,
matching the pattern from mig 082, 099, 100, 103, 106, 110, 127, 129.

internal/db/migrations/134_berufung_unification.down.sql

@@ -9,6 +9,16 @@
 -- never deleted them — that's what makes this down-migration safe).
 -- ---------------------------------------------------------------
 
+-- ---------------------------------------------------------------
+-- 0. Audit reason (required by mig 079 trigger — step 2 UPDATEs
+--    paliad.deadline_rules to reverse the reassignment).
+-- ---------------------------------------------------------------
+
+SELECT set_config(
+    'paliad.audit_reason',
+    'mig 134 DOWN: revert Slice B1 — restore 3 separate UPC appeal proceeding_types, drop applies_to_target column',
+    true);
+
 -- ---------------------------------------------------------------
 -- 1. Un-archive the 3 old appeal proceeding_types.
 -- ---------------------------------------------------------------