Fix wellness parser: field names, sleep epoch durations, HRV, sleep score

The Garmin FIT SDK returns snake_case field names but the parser was
looking for camelCase. Sleep epoch durations were wrong (fixed 30s each
instead of computing from timestamp gaps). HRV is in message 370 not 275
(275 now carries sleep levels in modern firmware). Multiple fixes:

- msg 55: use 'steps', 'heart_rate', 'active_calories' (not numeric keys)
- msg 211: use 'resting_heart_rate' (not msg.get(0))
- msg 227: use 'stress_level_time'/'stress_level_value' for named fields
- msg 132: use snake_case 'stress_level_time'/'stress_level_value'
- msg 275: detect sleep_level field → handle as sleep epoch (modern),
           fall back to HRV handling for older firmware
- msg 370: new handler for modern hrv_status_summary (last_night_average,
           last_night_5_min_high, status)
- msg 346: new handler for sleep_assessment → overall_sleep_score
- msg 21:  new handler for sleep session start/stop events to close the
           last sleep epoch and record sleep_start/sleep_end timestamps
- Sleep duration: computed from epoch timestamp gaps instead of 30s/epoch
- Celery task SQL: add sleep_score, sleep_start, sleep_end to INSERT/UPDATE;
  use GREATEST for total_calories so most-complete value wins across files

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

backend/app/workers/tasks.py

@@ -215,11 +215,13 @@ def parse_wellness_fit(file_path: str, user_id: int):
                 INSERT INTO health_metrics (user_id, date, resting_hr, avg_hr_day, max_hr_day,
                     avg_stress, spo2_avg, hrv_nightly_avg, hrv_5min_high, hrv_status,
                     steps, floors_climbed, active_calories, total_calories,
-                    sleep_duration_s, sleep_deep_s, sleep_light_s, sleep_rem_s, sleep_awake_s)
+                    sleep_duration_s, sleep_deep_s, sleep_light_s, sleep_rem_s, sleep_awake_s,
+                    sleep_score, sleep_start, sleep_end)
                 VALUES (:user_id, :date, :resting_hr, :avg_hr, :max_hr,
                     :avg_stress, :spo2_avg, :hrv_avg, :hrv_high, :hrv_status,
                     :steps, :floors, :active_cal, :total_cal,
-                    :sleep_dur, :sleep_deep, :sleep_light, :sleep_rem, :sleep_awake)
+                    :sleep_dur, :sleep_deep, :sleep_light, :sleep_rem, :sleep_awake,
+                    :sleep_score, :sleep_start, :sleep_end)
                 ON CONFLICT (user_id, date) DO UPDATE SET
                     resting_hr       = COALESCE(EXCLUDED.resting_hr, health_metrics.resting_hr),
                     avg_hr_day       = COALESCE(EXCLUDED.avg_hr_day, health_metrics.avg_hr_day),
@@ -232,12 +234,15 @@ def parse_wellness_fit(file_path: str, user_id: int):
                     steps            = COALESCE(EXCLUDED.steps, health_metrics.steps),
                     floors_climbed   = COALESCE(EXCLUDED.floors_climbed, health_metrics.floors_climbed),
                     active_calories  = COALESCE(EXCLUDED.active_calories, health_metrics.active_calories),
-                    total_calories   = COALESCE(EXCLUDED.total_calories, health_metrics.total_calories),
+                    total_calories   = GREATEST(EXCLUDED.total_calories, health_metrics.total_calories),
                     sleep_duration_s = COALESCE(EXCLUDED.sleep_duration_s, health_metrics.sleep_duration_s),
                     sleep_deep_s     = COALESCE(EXCLUDED.sleep_deep_s, health_metrics.sleep_deep_s),
                     sleep_light_s    = COALESCE(EXCLUDED.sleep_light_s, health_metrics.sleep_light_s),
                     sleep_rem_s      = COALESCE(EXCLUDED.sleep_rem_s, health_metrics.sleep_rem_s),
-                    sleep_awake_s    = COALESCE(EXCLUDED.sleep_awake_s, health_metrics.sleep_awake_s)
+                    sleep_awake_s    = COALESCE(EXCLUDED.sleep_awake_s, health_metrics.sleep_awake_s),
+                    sleep_score      = COALESCE(EXCLUDED.sleep_score, health_metrics.sleep_score),
+                    sleep_start      = COALESCE(EXCLUDED.sleep_start, health_metrics.sleep_start),
+                    sleep_end        = COALESCE(EXCLUDED.sleep_end, health_metrics.sleep_end)
             """), {
                 "user_id": user_id, "date": date_dt,
                 "resting_hr": data.get("resting_hr"),
@@ -257,6 +262,9 @@ def parse_wellness_fit(file_path: str, user_id: int):
                 "sleep_light": data.get("sleep_light_s"),
                 "sleep_rem": data.get("sleep_rem_s"),
                 "sleep_awake": data.get("sleep_awake_s"),
+                "sleep_score": data.get("sleep_score"),
+                "sleep_start": data.get("sleep_start"),
+                "sleep_end": data.get("sleep_end"),
             })
         db.commit()