Add segments, YTD stats, route matching fixes, body battery layout, pace fix

- Segments page: new /segments route with auto-generate (1km splits, turn
  detection, hill detection), manual segment creation, per-segment performance
  times across matched activities; fixed auth on existing segment endpoints
- YTD distance: new /activities/stats/ytd endpoint; Dashboard replaces
  'Total distance' with 'Running this year' + 'Cycling this year'; Activities
  page shows YTD stats row
- Weekly chart click: clicking a Dashboard bar navigates to Activities filtered
  to that week; Activities reads from/to query params with dismissable chip
- Route matching: add ±2.5% distance gate + 3% relative DTW threshold
  (was flat 80m); tighten candidate pre-filter from 80/120% to 95/105%
- Body battery layout: HR chart and body battery now side-by-side at same
  height on large screens instead of stacked full-width
- Pace display fix: MetricTimeline clamps GPS speed outliers before computing
  Y-axis domain; tick formatter guards against v<=0 or v>25 m/s

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

backend/app/workers/tasks.py

@@ -314,6 +314,7 @@ def detect_route(activity_id: int, user_id: int):
             if route.reference_polyline and routes_are_similar(
                 new_act.polyline, route.reference_polyline,
                 new_act.bounding_box, route.bounding_box,
+                dist1=new_act.distance_m, dist2=route.distance_m,
             ):
                 new_act.named_route_id = route.id
                 db.commit()
@@ -326,8 +327,8 @@ def detect_route(activity_id: int, user_id: int):
                 Activity.named_route_id == None,
                 Activity.id != activity_id,
                 Activity.polyline != None,
-                Activity.distance_m >= (new_act.distance_m or 0) * 0.8,
-                Activity.distance_m <= (new_act.distance_m or 0) * 1.2,
+                Activity.distance_m >= (new_act.distance_m or 0) * 0.95,
+                Activity.distance_m <= (new_act.distance_m or 0) * 1.05,
             )
         ).scalars().all()
 
@@ -335,6 +336,7 @@ def detect_route(activity_id: int, user_id: int):
             if routes_are_similar(
                 new_act.polyline, candidate.polyline,
                 new_act.bounding_box, candidate.bounding_box,
+                dist1=new_act.distance_m, dist2=candidate.distance_m,
             ):
                 older = candidate if candidate.start_time < new_act.start_time else new_act
                 newer = new_act if candidate.start_time < new_act.start_time else candidate