fix: isolate ledger outbox delivery by instance

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

trex_core/adapters/persistence/sql/028_ledger_outbox_instance_claims.sql

@@ -0,0 +1,22 @@
+-- GitHub #84: persist outbox owner instance and add claim/lease fields so
+-- shared-DB daemon writers only deliver their own rows and can safely recover
+-- abandoned work after lease expiry. Existing rows remain fail-closed when the
+-- owner instance cannot be inferred.
+ALTER TABLE ledger_outbox ADD COLUMN IF NOT EXISTS instance_key TEXT;
+ALTER TABLE ledger_outbox ADD COLUMN IF NOT EXISTS claim_owner TEXT;
+ALTER TABLE ledger_outbox ADD COLUMN IF NOT EXISTS claim_expires_at TIMESTAMPTZ;
+
+UPDATE ledger_outbox
+SET instance_key='__unowned__'
+WHERE instance_key IS NULL;
+
+ALTER TABLE ledger_outbox ALTER COLUMN instance_key SET DEFAULT '__unowned__';
+ALTER TABLE ledger_outbox ALTER COLUMN instance_key SET NOT NULL;
+
+CREATE INDEX IF NOT EXISTS idx_ledger_outbox_instance_pending
+    ON ledger_outbox (instance_key, status, created_at)
+    WHERE status = 'pending';
+
+CREATE INDEX IF NOT EXISTS idx_ledger_outbox_instance_claim_expires
+    ON ledger_outbox (instance_key, claim_expires_at)
+    WHERE status = 'pending';