Fix overnight flag lost on Journal roundtrip

Three gaps in the Planner → Journal → Planner roundtrip:

1. SaveToJournalButton: wasn't including isDayBreak when building
   waypoints for GPX generation
2. PlannerMap GPX import: wasn't setting overnight on Y.Maps when
   importing waypoints with isDayBreak
3. use-yjs initial waypoints: wasn't setting overnight from isDayBreak

Also widened the waypoint type throughout the chain (api.sessions,
session.$id, SessionView, extractWaypoints) to carry isDayBreak.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/planner/app/components/PlannerMap.tsx

@@ -411,6 +411,8 @@ export function PlannerMap({ yjs, onRouteRequest, highlightPosition, onImportErr
           const yMap = new Y.Map();
           yMap.set("lat", wp.lat);
           yMap.set("lon", wp.lon);
+          if (wp.name) yMap.set("name", wp.name);
+          if (wp.isDayBreak) yMap.set("overnight", true);
           yjs.waypoints.push([yMap]);
         }