feat(map): mobile fullscreen button on trip page map

Button in bottom-right of #trip-map (z-index:1000), hidden ≥769px.
Attribution moved to bottom-left to free the corner. Clicking toggles
.is-fullscreen on .home-map-col (position:fixed, 100dvh), locks body
scroll, and calls tripMap.resize() for MapLibre to re-render.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vgmzx8VTTTmCskSpQtsLTr

themes/intotheeast/css/style.css

@@ -929,10 +929,22 @@ body::after {
 }
 
 .home-map {
+    position: relative;
     width: 100%;
     height: 100%;
 }
 
+.home-map-col.is-fullscreen {
+    position: fixed !important;
+    inset: 0;
+    z-index: 9999;
+    height: 100dvh !important;
+}
+
+.home-map-col.is-fullscreen .home-map {
+    height: 100dvh;
+}
+
 .home-feed-col {
     padding: var(--space-8) var(--space-8);
 }