V3-07: route drawing (pins and straight lines)

Route plans are their own entity (RoutePlan/Waypoint, schema v3), never joined into ride totals or the rides list. RoutePlanRepository recomputes straight-line distance after every waypoint mutation. RoutePlannerScreen supports tap-to-add, tap-to-delete, and hand-rolled drag-to-move via MapCamera's screen/latlng conversions.

Fixed a real bug found by testing: FlutterMap's initialCenter/initialZoom are read once at construction, so building the map before the waypoints stream's first emission froze the camera on null-island. Also documents a genuine ten-minute test hang traced to Stream.first on a Drift watch() query inside testWidgets, which needs a pump-driven Timer that flutter_test's fake zone never advances on its own.

docs/v3/README.md

@@ -23,7 +23,7 @@ backup are v4 — see [../BACKLOG.md](../BACKLOG.md).
 | [V3-04](V3-04-live-map.md) | Live map on the recording screen | M | — | Done |
 | [V3-05](V3-05-mounted-mode.md) | Mounted (handlebar) mode | M | V3-04 | Done |
 | [V3-06](V3-06-notification-stats.md) | Live stats in the notification | S | — | Done |
-| [V3-07](V3-07-route-drawing.md) | Route drawing (pins, straight lines) | M | — | Not started |
+| [V3-07](V3-07-route-drawing.md) | Route drawing (pins, straight lines) | M | — | Done |
 | [V3-08](V3-08-road-routing.md) | Road-snapped routing and ETA | L | V3-07, V3-01 | Not started |
 | [V3-09](V3-09-route-following.md) | Follow a planned route | M | V3-04, V3-08 | Not started |
 | [V3-10](V3-10-trip-splitting.md) | Trip splitting | S | — | Not started |