Chat template with Aspire loses ingestion state on every app restart

Because it's using Aspire's SQLite hosting:

```cs
var ingestionCache = builder.AddSqlite("ingestionCache");
```

... it makes up a new random filename for the ingestion cache DB on every restart, and hence always has to re-ingest the content. This means that ingestion doesn't work as an incremental process as designed.

Ideally we'll remove the ingestion cache entirely in the next update, but if we can't, we should definitely fix this (e.g., by doing `builder.AddSqlite("ingestionCache", builder.AppHostDirectory, "ingestionCache.sqlite")`).