Batch 1: dashboard, maps, segments rewrite, health, sync UX

Fixes:
- Dashboard: featured most-recent activity card with map + stats
- Maps default to Street; preferCanvas + larger tile buffer for smoother pan/zoom
- Running cadence as colour-banded dots + 165 spm guide line
- Routes: inline row expansion, rename (PATCH /routes/{id}), podium + deltas, tiled map
- Records: remove reversed pace Y-axis
- Profile: remove resting HR; add goal weight
- Health: snapshot weight carry-forward; VO2 trend axis 30-70;
  weight goal line + kg/st-lb toggle + axis max; sleep 8h/avg lines
- Garmin sync progress moved to global store with persistent floating bar

Features:
- Speed-coloured activity route (default) with Speed/Solid toggle
- GPS-geometry segments: draw on map, match across all activities,
  1st/2nd/3rd leaderboard + podium badges (replaces old distance segments)
- Lap bests: best time per lap across a route + delta column
- Body Battery: highlight activity time windows

Schema: users.goal_weight_kg ALTER; new segments/segment_efforts tables.
Removes RouteSegment, the Segments page, and segment-bests endpoints.

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

backend/app/api/segments.py

@@ -0,0 +1,214 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy import select, func
+from pydantic import BaseModel
+from typing import Optional, List
+from datetime import datetime
+
+import polyline as polyline_lib
+
+from app.core.database import get_db
+from app.core.security import get_current_user
+from app.models.user import User, Segment, SegmentEffort, Activity, ActivityDataPoint
+from app.services.route_matcher import haversine_m
+
+router = APIRouter()
+
+
+class SegmentCreate(BaseModel):
+    name: str
+    activity_id: int
+    start_distance_m: float
+    end_distance_m: float
+
+
+class EffortOut(BaseModel):
+    activity_id: int
+    activity_name: str
+    date: Optional[datetime]
+    duration_s: float
+    rank: Optional[int]
+
+
+class SegmentOut(BaseModel):
+    id: int
+    name: str
+    sport_type: Optional[str]
+    polyline: Optional[str]
+    distance_m: Optional[float]
+    created_from_activity_id: Optional[int]
+    effort_count: int = 0
+    best_s: Optional[float] = None
+
+
+class SegmentDetailOut(SegmentOut):
+    leaderboard: List[EffortOut] = []
+
+
+class ActivitySegmentOut(BaseModel):
+    segment_id: int
+    name: str
+    polyline: Optional[str]
+    distance_m: Optional[float]
+    duration_s: float
+    rank: Optional[int]          # this activity's place on the leaderboard
+    best_s: Optional[float]      # current gold time
+    effort_count: int
+
+
+def _bbox(coords):
+    lats = [c[0] for c in coords]
+    lons = [c[1] for c in coords]
+    return {"min_lat": min(lats), "max_lat": max(lats), "min_lon": min(lons), "max_lon": max(lons)}
+
+
+async def _own_segment(segment_id: int, user_id: int, db: AsyncSession) -> Segment:
+    seg = (await db.execute(
+        select(Segment).where(Segment.id == segment_id, Segment.user_id == user_id)
+    )).scalar_one_or_none()
+    if not seg:
+        raise HTTPException(status_code=404, detail="Segment not found")
+    return seg
+
+
+@router.get("/", response_model=List[SegmentOut])
+async def list_segments(
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    segs = (await db.execute(
+        select(Segment).where(Segment.user_id == current_user.id).order_by(Segment.created_at.desc())
+    )).scalars().all()
+    out = []
+    for s in segs:
+        agg = (await db.execute(
+            select(func.count(SegmentEffort.id), func.min(SegmentEffort.duration_s))
+            .where(SegmentEffort.segment_id == s.id)
+        )).one()
+        out.append(SegmentOut(
+            id=s.id, name=s.name, sport_type=s.sport_type, polyline=s.polyline,
+            distance_m=s.distance_m, created_from_activity_id=s.created_from_activity_id,
+            effort_count=agg[0] or 0, best_s=agg[1],
+        ))
+    return out
+
+
+@router.post("/", response_model=SegmentOut)
+async def create_segment(
+    body: SegmentCreate,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    activity = (await db.execute(
+        select(Activity).where(Activity.id == body.activity_id, Activity.user_id == current_user.id)
+    )).scalar_one_or_none()
+    if not activity:
+        raise HTTPException(status_code=404, detail="Activity not found")
+
+    lo, hi = sorted((body.start_distance_m, body.end_distance_m))
+    dps = (await db.execute(
+        select(ActivityDataPoint)
+        .where(ActivityDataPoint.activity_id == activity.id)
+        .order_by(ActivityDataPoint.timestamp)
+    )).scalars().all()
+
+    coords = [
+        (p.latitude, p.longitude)
+        for p in dps
+        if p.distance_m is not None and p.latitude is not None and p.longitude is not None
+        and lo <= p.distance_m <= hi
+    ]
+    if len(coords) < 2:
+        raise HTTPException(status_code=400, detail="Selected range has too few GPS points")
+
+    seg = Segment(
+        user_id=current_user.id,
+        name=body.name.strip() or "Segment",
+        sport_type=activity.sport_type,
+        polyline=polyline_lib.encode(coords),
+        start_lat=coords[0][0], start_lng=coords[0][1],
+        end_lat=coords[-1][0], end_lng=coords[-1][1],
+        distance_m=max(0.0, hi - lo),
+        bounding_box=_bbox(coords),
+        created_from_activity_id=activity.id,
+    )
+    db.add(seg)
+    await db.commit()
+    await db.refresh(seg)
+
+    # Match across all activities in the background.
+    from app.workers.tasks import match_segment
+    match_segment.delay(seg.id)
+
+    return SegmentOut(
+        id=seg.id, name=seg.name, sport_type=seg.sport_type, polyline=seg.polyline,
+        distance_m=seg.distance_m, created_from_activity_id=seg.created_from_activity_id,
+        effort_count=0, best_s=None,
+    )
+
+
+@router.get("/by-activity/{activity_id}", response_model=List[ActivitySegmentOut])
+async def segments_for_activity(
+    activity_id: int,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """Segments that this activity has an effort on, with the activity's place + the gold time."""
+    rows = (await db.execute(
+        select(Segment, SegmentEffort)
+        .join(SegmentEffort, SegmentEffort.segment_id == Segment.id)
+        .where(Segment.user_id == current_user.id, SegmentEffort.activity_id == activity_id)
+        .order_by(Segment.created_at.desc())
+    )).all()
+
+    out = []
+    for seg, effort in rows:
+        agg = (await db.execute(
+            select(func.count(SegmentEffort.id), func.min(SegmentEffort.duration_s))
+            .where(SegmentEffort.segment_id == seg.id)
+        )).one()
+        out.append(ActivitySegmentOut(
+            segment_id=seg.id, name=seg.name, polyline=seg.polyline, distance_m=seg.distance_m,
+            duration_s=effort.duration_s, rank=effort.rank,
+            best_s=agg[1], effort_count=agg[0] or 0,
+        ))
+    return out
+
+
+@router.get("/{segment_id}", response_model=SegmentDetailOut)
+async def get_segment(
+    segment_id: int,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    seg = await _own_segment(segment_id, current_user.id, db)
+    rows = (await db.execute(
+        select(SegmentEffort, Activity)
+        .join(Activity, Activity.id == SegmentEffort.activity_id)
+        .where(SegmentEffort.segment_id == seg.id)
+        .order_by(SegmentEffort.duration_s)
+    )).all()
+    leaderboard = [
+        EffortOut(
+            activity_id=e.activity_id, activity_name=a.name,
+            date=e.achieved_at or a.start_time, duration_s=e.duration_s, rank=e.rank,
+        )
+        for e, a in rows
+    ]
+    return SegmentDetailOut(
+        id=seg.id, name=seg.name, sport_type=seg.sport_type, polyline=seg.polyline,
+        distance_m=seg.distance_m, created_from_activity_id=seg.created_from_activity_id,
+        effort_count=len(leaderboard), best_s=leaderboard[0].duration_s if leaderboard else None,
+        leaderboard=leaderboard,
+    )
+
+
+@router.delete("/{segment_id}", status_code=204)
+async def delete_segment(
+    segment_id: int,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    seg = await _own_segment(segment_id, current_user.id, db)
+    await db.delete(seg)
+    await db.commit()