feat(portfolio): nest asset positions

docs/deploy-coolify-selfhosted.md

@@ -101,12 +101,14 @@ Successful GIF replies include the result behind Telegram spoiler formatting.
 > counts and creates indexes on startup. Deleted legacy command rows are
 > retained with `deleted: true`; `/stats` queries filter those rows from visible
 > results. A historical `system` collection may remain in MongoDB with completed
-> migration records. Stock and coin documents store `costBasis` by symbol. On
-> every startup, enabled paper-trading modules verify that each positive holding
-> has a valid basis; legacy holdings are initialized from current quotes before
-> Telegram handlers are installed. The bot intentionally fails startup if a
-> required quote or migration write fails. Completed records remain in `system`
-> as audit history, but do not suppress later invariant scans.
+> migration records. Stock stores cash as `vnd`; coin stores cash as `usd`.
+> Both embed positions as
+> `assets.<symbol>.{quantity,base,dividendCheckedAt}`. On every startup, enabled
+> paper-trading modules verify this shape and migrate the previous flat
+> `assets`/`costBasis` documents before Telegram handlers are installed. The bot
+> intentionally fails startup if validation or a migration write fails.
+> Completed records remain in `system` as audit history, but do not suppress
+> later invariant scans.
 
 ## 2. Coolify