Cut Garmin sync API volume; dashboard/health/records/UI improvements

Garmin Connect sync:
- Incremental syncs now re-fetch only a 1-day buffer (yesterday + today)
  instead of the full lookback window every run. Full lookback applies on
  the first sync only. Cuts steady-state API calls ~10x.
- Beat interval is now configurable via GARMIN_SYNC_INTERVAL_MINUTES and
  surfaced to the UI; the sync toggle is relabelled to the real cadence.

Frontend:
- Collapsible sidebar; clearer logged-in user + role display.
- Unified Body Battery colouring between dashboard and health (shared util).
- Sleep score trend chart on health page.
- Segments + medals on the dashboard's most-recent activity.
- Segments tab on the Records page.

Repo hygiene: add .gitignore, untrack committed __pycache__/*.pyc.

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

backend/app/api/garmin_sync.py

@@ -7,6 +7,7 @@ from datetime import datetime
 
 from app.core.database import get_db
 from app.core.security import get_current_user
+from app.core.config import settings
 from app.models.user import User, GarminConnectConfig
 
 router = APIRouter()
@@ -27,6 +28,7 @@ class GarminConfigOut(BaseModel):
     sync_activities: bool
     sync_wellness: bool
     sync_lookback_days: int
+    sync_interval_minutes: int           # how often the automatic sync runs
     last_sync_at: Optional[datetime]
     last_sync_status: Optional[str]
     connected: bool
@@ -48,6 +50,7 @@ async def get_config(
         return GarminConfigOut(
             email="", sync_enabled=False, sync_activities=True,
             sync_wellness=True, sync_lookback_days=30,
+            sync_interval_minutes=settings.garmin_sync_interval_minutes,
             last_sync_at=None, last_sync_status=None, connected=False,
         )
     return GarminConfigOut(
@@ -56,6 +59,7 @@ async def get_config(
         sync_activities=cfg.sync_activities,
         sync_wellness=cfg.sync_wellness,
         sync_lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
+        sync_interval_minutes=settings.garmin_sync_interval_minutes,
         last_sync_at=cfg.last_sync_at,
         last_sync_status=cfg.last_sync_status,
         connected=True,
@@ -121,6 +125,7 @@ async def save_config(
         sync_activities=cfg.sync_activities,
         sync_wellness=cfg.sync_wellness,
         sync_lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
+        sync_interval_minutes=settings.garmin_sync_interval_minutes,
         last_sync_at=cfg.last_sync_at,
         last_sync_status=cfg.last_sync_status,
         connected=True,