fix(api): support generic Nd period presets (90d, 365d, …)

_preset_to_range only special-cased today/30d/custom and fell through to 7d for
everything else, so the Fuel Log tab's default "90d" silently returned 7 days.
Parse any positive `Nd` preset into a today-(N-1)..today window. Backward-
compatible: today/30d/custom and the 7d default are unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

dashboard_api_rev.py

@@ -356,6 +356,9 @@ def _preset_to_range(period: str | None, start_date, end_date):
             except ValueError:
                 return default
         return _d(start_date, today), _d(end_date, today)
+    # generic 'Nd' window (e.g. 7d / 30d / 90d / 365d) — used by the Fuel Log tab
+    if p.endswith("d") and p[:-1].isdigit() and int(p[:-1]) > 0:
+        return today - timedelta(days=int(p[:-1]) - 1), today
     # default + '7d'
     return today - timedelta(days=6), today