Add body battery: sync, storage, and health UI chart

Parses Garmin Connect get_body_battery() per day, storing charged/drained/
start+end levels and the fine-grained [[ts_ms, level, type, stress]] values
array in a new body_battery JSONB column on health_metrics.

Frontend adds:
- BatteryRing SVG gauge (color-scaled 0–100)
- BodyBatteryChart: ComposedChart with type-colored bars (REST/ACTIVE/SLEEP/
  STRESS) and battery level overlay line, matching Garmin's layout
- Body battery trend chart in the Trends section (end_level per day)

Also adds avg_hr_day and weight data which now correctly sync with the
intraday_hr JSON serialization fix from the previous commit.

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

backend/app/services/garmin_connect_sync.py

@@ -202,6 +202,7 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
     processed = 0
 
     import time as _time
+    import json as _json
     for i in range(max(days, 1)):
         day = start_date + timedelta(days=i)
         day_str = day.isoformat()
@@ -212,6 +213,7 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
         # Intraday HR (requires display_name; skip gracefully if absent)
         hr_raw  = _safe(garmin.get_heart_rates, day_str) if garmin.display_name else None
         bc_data = _safe(garmin.get_body_composition, day_str, day_str)
+        bb_raw  = _safe(garmin.get_body_battery, day_str, day_str)
         _time.sleep(0.25)   # avoid hammering Garmin's wellness API
 
         row = _parse_day(stats, sleep_data, hrv_data)
@@ -243,6 +245,12 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
                 bwf = float(bw)
                 _set(row, "weight_kg", round(bwf / 1000 if bwf > 300 else bwf, 2))
 
+        # Body battery — store summary + fine-grained timeline
+        if bb_raw:
+            bb = _parse_body_battery(bb_raw, day_str)
+            if bb:
+                row["body_battery"] = _json.dumps(bb)
+
         # Intraday heart rate — store non-null [epoch_ms, bpm] pairs
         if hr_raw:
             raw_vals = hr_raw.get("heartRateValues") or []
@@ -253,11 +261,12 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
         if not row:
             continue
 
-        # psycopg2 treats Python lists as PostgreSQL arrays; serialize JSON columns
-        # explicitly so they arrive as a JSON string that the json/jsonb column accepts.
-        import json as _json
-        if "intraday_hr" in row and isinstance(row["intraday_hr"], list):
+        # psycopg2 treats Python lists/dicts as PG arrays/hstore; serialize JSON
+        # columns as strings so psycopg2 passes them correctly to json/jsonb columns.
+        if "intraday_hr" in row and not isinstance(row["intraday_hr"], str):
             row["intraday_hr"] = _json.dumps(row["intraday_hr"])
+        if "body_battery" in row and not isinstance(row["body_battery"], str):
+            row["body_battery"] = _json.dumps(row["body_battery"])
 
         cols = list(row.keys())
         col_sql  = ", ".join(cols)
@@ -288,6 +297,54 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
     return processed
 
 
+def _parse_body_battery(bb_response, day_str: str):
+    """Parse get_body_battery() response for a single day into a compact dict."""
+    if not bb_response:
+        return None
+    entry = next((e for e in bb_response if e.get("date") == day_str), None)
+    if not entry and bb_response:
+        entry = bb_response[0]
+    if not entry:
+        return None
+
+    charged    = entry.get("charged")
+    drained    = entry.get("drained")
+    start_lvl  = entry.get("startValue")
+    end_lvl    = entry.get("endValue")
+
+    # Fine-grained timeline: [[ts_ms, level, type_code, stress], ...]
+    # type_code: 0=REST, 1=ACTIVE, 2=SLEEP, 3=STRESS, 4=UNMEASURABLE
+    values = entry.get("bodyBatteryValuesArray") or []
+
+    if not values:
+        # Fall back to bodyBatteryStatList (segment-level data)
+        type_map = {"REST": 0, "ACTIVE": 1, "SLEEP": 2, "STRESS": 3, "UNMEASURABLE": 4}
+        for seg in (entry.get("bodyBatteryStatList") or []):
+            ts_str = seg.get("startTimestampGMT") or seg.get("startTimestampLocal")
+            if ts_str:
+                try:
+                    from datetime import datetime as _dt, timezone as _tz
+                    ts = _dt.fromisoformat(ts_str.rstrip("Z")).replace(tzinfo=_tz.utc)
+                    type_code = type_map.get(seg.get("activityType", "UNMEASURABLE"), 4)
+                    values.append([int(ts.timestamp() * 1000),
+                                   int(seg.get("bodyBatteryLevel") or 0),
+                                   type_code,
+                                   int(seg.get("stressLevel") or -1)])
+                except Exception:
+                    pass
+
+    if charged is None and end_lvl is None and not values:
+        return None
+
+    return {
+        "charged":     charged,
+        "drained":     drained,
+        "start_level": start_lvl,
+        "end_level":   end_lvl,
+        "values":      values,   # stripped from list-API, returned in intraday endpoint
+    }
+
+
 def _safe(fn, *args):
     try:
         return fn(*args)