M8-R03B: keep meter swap recompute in caller transaction

app/api/routes/api/meters.py

@@ -151,7 +151,7 @@ def _trigger_recompute(db: Session, start: datetime, label: str) -> int:
         # started_at is in the future — nothing to recompute.
         logger.info("%s: started_at (%s) is in the future, skipping recompute.", label, start)
         return 0
-    n = recompute_range(db, start, end)
+    n = recompute_range(db, start, end, commit=False)
     logger.info(
         "%s: recomputed %d period(s) in window [%s, %s).",
         label,
@@ -352,23 +352,27 @@ def patch_energy_meter(
             note=body.note,
             started_at=new_started_at_utc,
         )
+
+        # Retroactive recompute if started_at was changed.
+        if new_started_at_utc is not None and old_started_at is not None:
+            # Normalise old_started_at to UTC-aware for comparison.
+            if old_started_at.tzinfo is None:
+                old_started_at = old_started_at.replace(tzinfo=UTC)
+            # Window = [min(old, new), now) — covers all periods whose attribution
+            # may have changed due to the boundary shift in either direction.
+            window_start = min(old_started_at, new_started_at_utc)
+            _trigger_recompute(db, window_start, f"PATCH /api/energy/meters/{meter_id}")
+
+        db.commit()
     except MeterIntervalError as exc:
+        db.rollback()
         raise HTTPException(
             status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
             detail=str(exc),
         )
-
-    # Retroactive recompute if started_at was changed.
-    if new_started_at_utc is not None and old_started_at is not None:
-        # Normalise old_started_at to UTC-aware for comparison.
-        if old_started_at.tzinfo is None:
-            old_started_at = old_started_at.replace(tzinfo=UTC)
-        # Window = [min(old, new), now) — covers all periods whose attribution
-        # may have changed due to the boundary shift in either direction.
-        window_start = min(old_started_at, new_started_at_utc)
-        _trigger_recompute(db, window_start, f"PATCH /api/energy/meters/{meter_id}")
-
-    db.commit()
+    except Exception:
+        db.rollback()
+        raise
     db.refresh(meter)
 
     # Trigger HA discovery re-publish so label renames on the active meter