feat: use endpointUri for cross-route drill-down instead of label parsing

Server:
- Add endpointUri to PositionedNode (from RouteNode)
- Add fromEndpointUri to RouteSummary (catalog API)
- Catalog controller resolves endpoint URI from diagram store

UI:
- Build endpointRouteMap from catalog's fromEndpointUri field
- Drill-down uses exact match on node.endpointUri against the map
- Remove label parsing heuristics (extractTargetEndpoint, camelToKebab)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/dto/RouteSummary.java

@@ -9,5 +9,7 @@ import java.time.Instant;
 public record RouteSummary(
         @NotNull String routeId,
         @NotNull long exchangeCount,
-        Instant lastSeen
+        Instant lastSeen,
+        @Schema(description = "The from() endpoint URI, e.g. 'direct:processOrder'")
+        String fromEndpointUri
 ) {}