feat: enhance canvas styling and edge handling with glow effects

- Added custom CSS variables for edge stroke and connection line styles in light and dark modes to improve visual consistency.
- Updated edge rendering logic to utilize new styles, enhancing the appearance of temporary edges during interactions.
- Introduced a new utility function for applying glow effects based on source node types, improving the visual feedback of connections.
- Refactored edge mapping to support glow effects, enhancing user experience during node interactions.

app/globals.css

@@ -145,6 +145,23 @@
 }
 
 @layer components {
+  /* Kanten: doppelte Standard-Dicke, feste Kontrastfarben je Light/Dark (gleiches Schema wie colorMode) */
+  .react-flow {
+    --xy-edge-stroke: rgba(44, 62, 80, 1);
+    --xy-edge-stroke-width: 2;
+    --xy-edge-stroke-selected: rgba(44, 62, 80, 1);
+    --xy-connectionline-stroke: rgba(44, 62, 80, 1);
+    --xy-connectionline-stroke-width: 1;
+  }
+
+  .react-flow.dark {
+    --xy-edge-stroke: rgba(189, 195, 199, 1);
+    --xy-edge-stroke-width: 2;
+    --xy-edge-stroke-selected: rgba(189, 195, 199, 1);
+    --xy-connectionline-stroke: rgba(189, 195, 199, 1);
+    --xy-connectionline-stroke-width: 1;
+  }
+
   /* Verbindungs-Punkte über Node-Inhalt (XYFlow setzt kein z-index) */
   .react-flow__handle {
     z-index: 50;
@@ -156,9 +173,16 @@
   }
 
   .react-flow__edge.temp .react-flow__edge-path {
-    stroke: hsl(var(--foreground) / 0.3);
-    stroke-width: 2.5;
+    stroke-width: 5;
     stroke-dasharray: 8 6;
     stroke-linecap: round;
   }
+
+  .react-flow:not(.dark) .react-flow__edge.temp .react-flow__edge-path {
+    stroke: rgba(44, 62, 80, 0.35);
+  }
+
+  .react-flow.dark .react-flow__edge.temp .react-flow__edge-path {
+    stroke: rgba(189, 195, 199, 0.35);
+  }
 }