Alpaca returns 404 when you don't hold a position in a ticker.
The ingestion worker was logging this as an error and incrementing
the failure count. Now returns an empty items list instead, since
'no position' is a valid state, not an error.
The alpaca.url config file contains https://paper-api.alpaca.markets/v2
but the adapter code also prepends /v2/ to all paths, resulting in
/v2/v2/positions which returns 404. Now strips trailing /v2 or /v1
from the configured base URL since the adapter manages API versioning.
This was causing 1,017 consecutive broker sync failures.
Celes Renata