fix repeatable migrations

db/routines/R__006_fn_deye_clock_drift_sec.sql

@@ -0,0 +1,16 @@
+create or replace function ems.fn_deye_clock_drift_sec(
+  p_device_ts timestamptz,
+  p_reference_ts timestamptz
+)
+returns int
+language sql
+immutable
+as $fn$
+  select case
+    when p_device_ts is null or p_reference_ts is null then null::int
+    else abs(extract(epoch from (p_device_ts - p_reference_ts)))::int
+  end;
+$fn$;
+
+comment on function ems.fn_deye_clock_drift_sec(timestamptz, timestamptz) is
+  'Absolutní odchylka hodin Deye vs referenční UTC (sekundy).';