Cut climb profile sections in the backend

The chart steps are computed in Go and shipped as finished sections, next to
the profile statistics the climb package already owns: climb.ProfileSections
cuts a Route at its widest bends under a ProfilePolicy, and
rideanalysis.MergeClimbProfile takes over the merge that lived in
web/climbs.go, so web only loads the attempt rides and maps the DTOs.

The payload carries sections instead of raw elevations, and the browser keeps
what needs the canvas: slope bands, labels, distance ticks and colours.
official-climb-profile-logic.ts and its tests are gone, replaced by
climb/profile_test.go and a page test reading the embedded profile JSON.

1 files changed, 10 insertions, 0 deletions

diff --git a/climb/route.go b/climb/route.go
index 4ef3465..e341bea 100644
--- a/climb/route.go
+++ b/climb/route.go
@@ -14,6 +14,16 @@ type SegmentSample struct {
 	ElevationGainM float64
 }
 
+// Slice returns the sub-route covering the given point indices (inclusive). A route without coords
+// (a resampled profile) keeps them empty.
+func (route Route) Slice(start, end int) Route {
+	sliced := Route{Distances: route.Distances[start : end+1], Elevations: route.Elevations[start : end+1]}
+	if len(route.Coords) == len(route.Distances) {
+		sliced.Coords = route.Coords[start : end+1]
+	}
+	return sliced
+}
+
 // Sample returns the recorded length and elevation gain of the route slice between start and end (inclusive), counting only upward steps in the gain.
 func (route Route) Sample(start, end int) SegmentSample {
 	sample := SegmentSample{DistanceM: route.Distances[end] - route.Distances[start]}