feat(03-01): populate calendarEvents.objectUrl in sync.ts from obj.url

- Set objectUrl: obj.url ?? null in both .values() and .onDuplicateKeyUpdate({ set: {} })
  alongside existing etag assignment — stores CalDAV object URL for If-Match on
  update/delete (D-08)
- All existing broker/sync tests pass (47 total)

apps/api/src/broker/sync.ts

@@ -106,6 +106,7 @@ export async function syncCalendar(
         calendarId: cal.id,
         uid,
         etag: obj.etag ?? null,
+        objectUrl: obj.url ?? null,
         rawVevent: obj.data as string,
         dtstartUtc: dtstartUtcValue,
         dtstartDate: dtstartDateValue,
@@ -115,6 +116,7 @@ export async function syncCalendar(
       .onDuplicateKeyUpdate({
         set: {
           etag: obj.etag ?? null,
+          objectUrl: obj.url ?? null,
           rawVevent: obj.data as string,
           dtstartUtc: dtstartUtcValue,
           dtstartDate: dtstartDateValue,