Fix VO2 max extraction: values nested under entry['generic'] not top-level

The maxmet/daily range query returns entries shaped as:
  {"generic": {"calendarDate": "...", "vo2MaxPreciseValue": 42.7, ...}, ...}

The extractor was looking at the top level of each entry, finding nothing, and
falling through to the single-point training_status fallback every time.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

milevault_export/backend/app/services/garmin_connect_sync.py

@@ -345,11 +345,13 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
     except Exception as exc:
         logger.info("maxmet history fetch failed: %s", exc)
 
-    # Check whether the range query yielded any usable vo2max values
+    # Each entry has the vo2max data nested under entry["generic"]
+    def _extract_generic(entry):
+        return (entry.get("generic") or {}) if isinstance(entry, dict) else {}
+
     valid_from_range = any(
-        (entry.get("vo2MaxPreciseValue") or entry.get("vo2MaxValue") or 0)
-        for entry in mm_entries
-        if isinstance(entry, dict)
+        (_extract_generic(e).get("vo2MaxPreciseValue") or _extract_generic(e).get("vo2MaxValue") or 0)
+        for e in mm_entries
     )
 
     # Always fall back to training_status when the range query had no valid data
@@ -359,17 +361,16 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
         v = generic.get("vo2MaxPreciseValue") or generic.get("vo2MaxValue")
         logger.info("training_status vo2max=%s at %s", v, generic.get("calendarDate"))
         if v and float(v) > 0:
-            mm_entries = [{"calendarDate": generic.get("calendarDate") or today_str,
-                           "vo2MaxPreciseValue": float(v)}]
+            mm_entries = [{"generic": {"calendarDate": generic.get("calendarDate") or today_str,
+                                       "vo2MaxPreciseValue": float(v)}}]
 
     stored = 0
     for entry in mm_entries:
-        if not isinstance(entry, dict):
-            continue
-        v = entry.get("vo2MaxPreciseValue") or entry.get("vo2MaxValue")
+        generic = _extract_generic(entry)
+        v = generic.get("vo2MaxPreciseValue") or generic.get("vo2MaxValue")
         if not v or float(v) <= 0:
             continue
-        entry_date = entry.get("calendarDate") or today_str
+        entry_date = generic.get("calendarDate") or today_str
         try:
             fa_row = {"vo2max": float(v)}
             if fa_age and entry_date == today_str: