Implements the journal-elevation-profile change (specs/journal-elevation-profile):
- gpx: `elevationSeries(tracks)` → { d, e, lat, lng }[] with cumulative distance,
downsampled (keeps first/last), empty when <2 points carry elevation.
- ElevationProfile: read-only SVG area chart (vertical gradient fill), highest/
lowest summary + a hover readout. Reports hovered index (onActive) and clicked
index (onSeek); draws a marker at the active index. Renders nothing for an
empty series.
- RouteMapThumbnail: ActiveMarker (CircleMarker at the chart's active point),
HoverTracker (route hover → nearest sample → onHoverIndex), Recenter (panTo on
chart click). Props forwarded through ClientMap.
- Wired into the activity + route detail pages via a shared activeIndex/centerOn
state; loaders expose the series (activity reuses the moving-time parse).
- i18n journal.elevation.{highest,lowest} in en + de.
Ascent/descent stay in the stat row (#532); the chart summary shows highest/
lowest to avoid duplication.
Tests: elevationSeries unit; ElevationProfile component (jsdom); e2e creates an
activity from an elevation GPX and asserts the chart renders. typecheck + lint +
unit (gpx 67, journal 315) green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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