fix: remove day from $setOnInsert — and $setOnInsert conflict on same path

MongoDB error: 'Updating the path day would create a conflict at day'.
On insert, $inc treats a missing field as 0, so no seed needed.

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/app/v1/consumption/daily/route.ts

@@ -11,9 +11,9 @@ export const dynamic = "force-dynamic";
  * (not a cumulative total), so each PUT adds to the day's running totals rather than
  * overwriting them. Lifetime is a snapshot — the latest one wins, so it is $set not $inc.
  *
- * $setOnInsert seeds the whole `day` subdocument as a nested object (not dotted paths)
- * because $inc and $setOnInsert cannot touch the same field — MongoDB rejects that with
- * a 500, which is what held the 20 cached chunks back.
+ * $setOnInsert must not touch `day` at all: $inc on `day.km` and $setOnInsert on `day`
+ * conflict in MongoDB ("Updating the path 'day' would create a conflict at 'day'").
+ * On an insert, $inc treats a missing field as 0 and adds to it, so no seed is needed.
  */
 export async function PUT(request: Request) {
   const denied = requireIngest(request);
@@ -38,9 +38,6 @@ export async function PUT(request: Request) {
         $set,
         $setOnInsert: {
           createdAt: updatedAt,
-          installationId: record.installationId,
-          date: record.date,
-          day: { km: 0, kwh: 0, hours: 0, socDrop: 0 },
         },
       },
       { upsert: true },