M2-T04: add single-row record CRUD API (patch/delete)

- PATCH/DELETE /api/locations/{person}/{datetime} and /api/poo/{timestamp}
- update only non-PK fields (PK immutable); 404 on missing PK
- delete scoped to exact full PK with rowcount guard (0->404, 1->ok);
  no batch/truncate/drop path
- session + CSRF protected; bare ingestion endpoints untouched
- service helpers in app/services/location.py and poo.py; regenerate openapi/
- tests/test_api_record_crud.py

app/services/location.py

@@ -1,6 +1,6 @@
 from datetime import datetime, timezone
 
-from sqlalchemy import insert
+from sqlalchemy import delete, insert, select
 from sqlalchemy.orm import Session
 
 from app.models.location import Location
@@ -40,3 +40,58 @@ def record_location(session: Session, payload: LocationRecordRequest) -> None:
     )
     session.execute(stmt)
     session.commit()
+
+
+def update_location(
+    session: Session,
+    person: str,
+    datetime_pk: str,
+    *,
+    latitude: float | None,
+    longitude: float | None,
+    altitude: float | None,
+) -> Location | None:
+    """Update non-PK fields of a single location row.
+
+    Returns the updated ORM object, or ``None`` if the PK does not exist.
+    The caller must not pass PK fields — they are immutable.
+    Only fields with a non-``None`` value are written; ``altitude`` being
+    ``None`` in the request means "leave unchanged", not "clear to NULL".
+    """
+    row = session.execute(
+        select(Location).where(
+            Location.person == person,
+            Location.datetime == datetime_pk,
+        )
+    ).scalar_one_or_none()
+
+    if row is None:
+        return None
+
+    if latitude is not None:
+        row.latitude = latitude
+    if longitude is not None:
+        row.longitude = longitude
+    if altitude is not None:
+        row.altitude = altitude
+
+    session.commit()
+    session.refresh(row)
+    return row
+
+
+def delete_location(session: Session, person: str, datetime_pk: str) -> bool:
+    """Delete the single location row identified by its full composite PK.
+
+    Returns ``True`` if exactly one row was deleted, ``False`` if the PK did
+    not exist (caller should raise 404).  The DELETE is scoped to the exact PK
+    — no batch/truncate path exists.
+    """
+    result = session.execute(
+        delete(Location).where(
+            Location.person == person,
+            Location.datetime == datetime_pk,
+        )
+    )
+    session.commit()
+    return result.rowcount == 1