Strava Heatmap, Per-Stage Trail Coloring & Elevation Gradient (v1.3.0 release)

This update adds Strava heatmap integration, per-stage trail coloring, an elevation-profile gradient view, richer activity metadata, resync, and several logbook UX improvements.

New Features

• Strava heatmap — New heatmap layer on the map, with auth handling and a DNR rule scoped to image loads so it doesn't break the heatmap page.
• Per-stage trail coloring — Trails on the Map Explorer are colored per stage.
• Elevation-profile gradient coloring — The elevation profile now reflects gradient.
• Extended activity metadata — More activity detail pulled from Strava.
• Resync Strava activity — Resync action for activities.

Improvements

• Sticky logbook actions bar; filter row no longer covered by the selected-actions toolbar.
• Added and updated tooltips in the logbook.
• Updated trail activity secondary menu.
• GPX export/import — export and import activities as GPX (richer in data).

Fixes

• GPX import activities as planned.