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/main.py

@@ -6,7 +6,7 @@ import asyncio
 
 from app.core.database import engine, AsyncSessionLocal, Base
 from app.core.config import settings
-from app.api import auth, activities, routes, health, records, upload, profile, garmin_sync, users
+from app.api import auth, activities, routes, health, records, upload, profile, garmin_sync, users, segments
 
 
 async def init_db():
@@ -82,17 +82,14 @@ async def init_db():
     except Exception as e:
         print(f"users.pocketid_allowed_group column migration skipped: {e}")
 
-    # route_segments auto_generated column added after initial creation
+    # goal_weight_kg column on users added after initial creation
     try:
         async with engine.begin() as conn:
             await conn.execute(text(
-                "ALTER TABLE route_segments ADD COLUMN IF NOT EXISTS auto_generated BOOLEAN DEFAULT FALSE"
-            ))
-            await conn.execute(text(
-                "ALTER TABLE route_segments ADD COLUMN IF NOT EXISTS auto_generated_type VARCHAR(20)"
+                "ALTER TABLE users ADD COLUMN IF NOT EXISTS goal_weight_kg FLOAT"
             ))
     except Exception as e:
-        print(f"route_segments column migration skipped: {e}")
+        print(f"users.goal_weight_kg column migration skipped: {e}")
 
     # Backfill avg_hr_day / max_hr_day from intraday_hr for Garmin Connect synced days
     try:
@@ -225,6 +222,7 @@ app.include_router(upload.router, prefix="/api/upload", tags=["upload"])
 app.include_router(profile.router, prefix="/api/profile", tags=["profile"])
 app.include_router(garmin_sync.router, prefix="/api/garmin-sync", tags=["garmin-sync"])
 app.include_router(users.router, prefix="/api/users", tags=["users"])
+app.include_router(segments.router, prefix="/api/segments", tags=["segments"])
 
 
 @app.get("/health")