fix repeatable migrations

db/routines/R__015_fn_ev_session_patch.sql

@@ -0,0 +1,49 @@
+create or replace function ems.fn_ev_session_apply_patch(
+  p_site_id int,
+  p_session_id int,
+  p_patch jsonb
+)
+returns jsonb
+language plpgsql
+as $fn$
+declare
+  v_id int;
+begin
+  if not (p_patch ? 'target_soc_pct') and not (p_patch ? 'target_deadline') then
+    return jsonb_build_object('success', false, 'error', 'no_fields');
+  end if;
+
+  update ems.ev_session es
+  set
+    target_soc_pct = case
+      when p_patch ? 'target_soc_pct' then
+        case
+          when p_patch->'target_soc_pct' is null
+            or jsonb_typeof(p_patch->'target_soc_pct') = 'null' then null
+          else (p_patch->>'target_soc_pct')::double precision
+        end
+      else es.target_soc_pct
+    end,
+    target_deadline = case
+      when p_patch ? 'target_deadline' then
+        case
+          when p_patch->'target_deadline' is null
+            or jsonb_typeof(p_patch->'target_deadline') = 'null' then null
+          else (p_patch->>'target_deadline')::timestamptz
+        end
+      else es.target_deadline
+    end
+  where es.id = p_session_id
+    and es.site_id = p_site_id
+  returning es.id into v_id;
+
+  if v_id is null then
+    return jsonb_build_object('success', false, 'session_id', null);
+  end if;
+
+  return jsonb_build_object('success', true, 'session_id', v_id);
+end;
+$fn$;
+
+comment on function ems.fn_ev_session_apply_patch(int, int, jsonb) is
+  'PATCH EV session – jen klíče přítomné v JSON (ISO string pro deadline).';