fix: compute GPX stats per-file to avoid spurious inter-track segments

Both stats.html.twig and trip.html.twig previously flattened all GPX
trackpoints into a single masterPts array before computing haversine
distance, elevation, and moving time. This caused the junction between
file N's last point and file N+1's first point to be treated as a real
segment — e.g. Florence→coast (~79 km, ~42 h) for Italy's 3-file demo
data, overstating distance and moving time significantly.

Fix: compute all metrics within each file independently and sum the
results. fileResults collection and callback consumption are unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WPJztrVGbwic2xTG7G9fjM

themes/intotheeast/templates/stats.html.twig

@@ -162,27 +162,24 @@ if (GPX_URLS.length > 0) {
                 });
                 fileResults[idx] = pts;
                 pending--;
-                if (pending === 0) { computeDistance(); }
+                if (pending === 0) { computeTotalDistance(); }
             })
             .catch(function(err) {
                 console.warn('GPX load failed:', url, err);
                 fileResults[idx] = [];
                 pending--;
-                if (pending === 0) { computeDistance(); }
+                if (pending === 0) { computeTotalDistance(); }
             });
     });
 
-    function computeDistance() {
-        var masterPts = [];
-        fileResults.forEach(function(pts) {
-            if (pts) { pts.forEach(function(p) { masterPts.push(p); }); }
-        });
+    function computeTotalDistance() {
         var total = 0;
-        for (var i = 1; i < masterPts.length; i++) {
-            total += haversine(masterPts[i-1].lat, masterPts[i-1].lon,
-                               masterPts[i].lat, masterPts[i].lon);
-        }
-        distEl.textContent = masterPts.length < 2 ? '—' : Math.round(total).toLocaleString();
+        fileResults.forEach(function(pts) {
+            for (var i = 1; i < pts.length; i++) {
+                total += haversine(pts[i-1].lat, pts[i-1].lon, pts[i].lat, pts[i].lon);
+            }
+        });
+        distEl.textContent = total > 0 ? Math.round(total).toLocaleString() : '—';
     }
 } else {
     // Mode B: sum haversine between consecutive entry lat/lng points