feat: expand trip inline stats to 6 stats + add cycling panel with GPX parsing

- Expanded stats block from 4 to 6 stats (days, entries, countries, cities, distance, temp range)
- Added date_end-aware days calculation (uses header.date_end when available)
- Added cities dedup logic (seen_city_lower) matching Task 1 pattern
- Added temperature range computation (temp_min / temp_max)
- Added has_gpx boolean flag
- Distance label is conditional: km cycled (GPX) vs km roamed (no GPX)
- Stats note text is conditional to match distance mode
- Cycling button added to filter bar (only rendered when has_gpx)
- Cycling panel (7 stat blocks) added after stats block (hidden by default, toggled independently)
- Replaced old haversine IIFE with unified haversineKm + parseGpxFiles + IIFE
- GPX Mode A: fetches GPX files, sums trackpoint distances, populates cycling panel
- GPX Mode B: haversine between entry GPS points (no GPX)
- Updated .trip-stats-grid from repeat(4) to repeat(3) columns
- Added .trip-cycling-block, .trip-cycling-header, .trip-cycling-icon, .trip-cycling-title, .trip-cycling-grid CSS

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

themes/intotheeast/css/style.css

@@ -990,7 +990,7 @@ body::after {
 
 .trip-stats-grid {
     display: grid;
-    grid-template-columns: repeat(4, 1fr);
+    grid-template-columns: repeat(3, 1fr);
     gap: var(--space-4);
     margin-bottom: var(--space-4);
 }
@@ -1010,6 +1010,43 @@ body::after {
     color: var(--color-ink-muted);
 }
 
+/* ── Trip page cycling panel ─────────────────────────────────────────────────── */
+
+.trip-cycling-block {
+    background: var(--color-canvas);
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius-md);
+    padding: var(--space-6);
+    margin-bottom: var(--space-6);
+}
+
+.trip-cycling-header {
+    display: flex;
+    align-items: center;
+    gap: var(--space-2);
+    margin-bottom: var(--space-4);
+}
+
+.trip-cycling-icon {
+    font-size: var(--text-xl);
+}
+
+.trip-cycling-title {
+    font-family: var(--font-display);
+    font-size: var(--text-lg);
+    color: var(--color-ink);
+}
+
+.trip-cycling-grid {
+    display: grid;
+    grid-template-columns: repeat(4, 1fr);
+    gap: var(--space-4);
+}
+
+@media (max-width: 600px) {
+    .trip-cycling-grid { grid-template-columns: repeat(2, 1fr); }
+}
+
 /* ── Story pages ─────────────────────────────────────────────────────────── */
 
 /* Override site-main constraints for story pages */