fix: set background color for unloaded map tile areas

Author: smartcmd

src/main/resources/web/index.html

@@ -23,7 +23,12 @@
         * { margin: 0; padding: 0; box-sizing: border-box; }
         html, body { height: 100%; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; background: var(--bg-color); }
 
-        #map { height: 100%; width: 100%; z-index: 1; }
+        #map { height: 100%; width: 100%; z-index: 1; background: var(--bg-color); }
+
+        /* Leaflet container background for unloaded tile areas */
+        .leaflet-container {
+            background: var(--bg-color);
+        }
 
         /* Optimize map tile rendering to prevent pixel blur */
         .leaflet-tile {