FUE-T03: correct meters POST docstring (no recomputed_periods field) and inaccurate test comments

app/api/routes/api/meters.py

@@ -185,9 +185,10 @@ def declare_energy_meter(
 
     **Retroactive recompute**: if ``started_at`` is in the past, billing
     records from that point forward are re-judged via ``recompute_range`` to
-    reflect the new meter attribution.  The response includes the count of
-    recomputed periods in ``recomputed_periods`` (not part of ``MeterResponse``
-    — the recompute is transparent; callers should re-fetch costs if needed).
+    reflect the new meter attribution.  The recompute is transparent — the
+    response body is the created meter (``MeterResponse``) only and does **not**
+    include a recompute count; callers should re-fetch costs if they need the
+    updated totals.
     """
     started_at_utc = _localize_started_at(body.started_at)