[Bug]: stock bars endpoint always returns unadjusted bar data

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Current Behavior

Setting `adjustmnet` param when querying historical bars returns unadjusted prices.

### Expected Behavior

The endpoint should return the correct corporate-actions-adjusted prices.

### SDK Version I encountered this issue in

0.42.0 (the bug seems to be in the API endpoint, not the python SDK)

### Steps To Reproduce

```markdown
export APCA_KEY=
export APCA_SEC=
curl -s -G "https://data.alpaca.markets/v2/stocks/bars" -H "APCA-API-KEY-ID: $APCA_KEY" -H "APCA-API-SECRET-KEY: $APCA_SEC" -d symbols=LAZR -d timeframe=1Day -d start=2026-06-25 -d end=2026-07-06 -d feed=sip -d adjustment=all | python3 -m json.tool

There is a huge price diff between 06-29 and 06-30, but the request uses `all` for `adjustment`.
```

### Filled out the Steps to Reproduce section?

- [x] I have entered valid steps to reproduce my issue or have attached a minimally reproducible case in code that shows my issue happening; and understand that without this my issue will be flagged as invalid and closed after 30 days.

### Anything else?

_No response_