Fix missing avg_hr_day/weight data; add 24hr HR chart to daily snapshot

Backend:
- main.py: add ADD COLUMN IF NOT EXISTS migrations for avg_hr_day, max_hr_day,
  and intraday_hr (JSONB) on health_metrics — these columns were in the model
  but missing from existing DB instances, silently dropping all avg/max HR data.
- models/user.py: add intraday_hr JSON column to HealthMetric.
- garmin_connect_sync.py: fetch body composition (weight, BMI, body fat, muscle
  mass) via get_body_composition() per day, with stats.bodyWeight as fallback.
  Fetch intraday heart rate via get_heart_rates() and store non-null
  [epoch_ms, bpm] pairs in intraday_hr.
- health.py: add GET /health-metrics/intraday?date=YYYY-MM-DD endpoint that
  returns the stored intraday_hr array for a specific day.

Frontend (HealthPage):
- Add IntradayHrChart component: AreaChart rendering the 24-hour HR trace
  with time-of-day x-axis.
- DailySnapshot: show 24-hour HR chart (when intraday data present) above
  the activity strip; add weight + body fat % to the Heart & HRV card;
  show max HR alongside avg HR.
- HealthPage: query /intraday for the selected day and pass data down.

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

backend/app/services/garmin_connect_sync.py

@@ -209,9 +209,47 @@ def sync_wellness(garmin, user_id: int, since: Optional[datetime], db,
         stats      = _safe(garmin.get_stats, day_str)
         sleep_data = _safe(garmin.get_sleep_data, day_str)
         hrv_data   = _safe(garmin.get_hrv_data, day_str)
+        # 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)
         _time.sleep(0.25)   # avoid hammering Garmin's wellness API
 
         row = _parse_day(stats, sleep_data, hrv_data)
+
+        # Weight + body composition from weight service (more reliable than stats)
+        if bc_data:
+            entries = (bc_data.get("dateWeightList")
+                       or bc_data.get("allWeightMetrics")
+                       or bc_data.get("weightList") or [])
+            if entries:
+                e = entries[0]
+                bw = e.get("weight")
+                if bw and float(bw) > 0:
+                    bwf = float(bw)
+                    _set(row, "weight_kg", round(bwf / 1000 if bwf > 300 else bwf, 2))
+                if e.get("bmi"):
+                    _set(row, "bmi", float(e["bmi"]))
+                if e.get("bodyFat"):
+                    _set(row, "body_fat_pct", float(e["bodyFat"]))
+                mm = e.get("muscleMass")
+                if mm and float(mm) > 0:
+                    mmf = float(mm)
+                    _set(row, "muscle_mass_kg", round(mmf / 1000 if mmf > 300 else mmf, 2))
+
+        # Weight from daily stats as fallback (present when Garmin scale is used)
+        if stats and "weight_kg" not in row:
+            bw = stats.get("bodyWeight")
+            if bw and float(bw) > 0:
+                bwf = float(bw)
+                _set(row, "weight_kg", round(bwf / 1000 if bwf > 300 else bwf, 2))
+
+        # Intraday heart rate — store non-null [epoch_ms, bpm] pairs
+        if hr_raw:
+            raw_vals = hr_raw.get("heartRateValues") or []
+            intraday = [[int(ts), int(v)] for ts, v in raw_vals if v is not None]
+            if intraday:
+                row["intraday_hr"] = intraday
+
         if not row:
             continue