Low-confidence detection filtering no longer enforced server-side

**File:** web/app.py:154

Server-side low-confidence detection filtering (present in the prior Cosmos-based code) appears to have been dropped, leaving it implemented only client-side in map.html's toggle.

**Failure scenario:** Any API consumer other than the bundled map JS -- a script hitting `/current`, `/history`, or `/history/area` directly -- now receives low-confidence (highest false-positive-rate) detections that used to be excluded server-side for every consumer. That invariant now depends entirely on client code the server doesn't control.

**Category:** correctness

Read web/app.py around line 154 and inspect how /current, /history, and /history/area handle detections, comparing them with the low-confidence rule described from the prior Cosmos-based code. Done means all three API endpoints exclude low-confidence detections independently of map.html's client-side toggle.

Written by the indexing model from the issue text.