refactor: unify "Executions" → "Exchanges" terminology

Rename all references from "Execution/executions/execCount" to
"Exchange/exchanges/exchangeCount" to align with Apache Camel's
native Exchange concept. Java class names (CamelExecutionException,
HttpOperationFailedException) are preserved as-is.

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

src/pages/RouteDetail/RouteDetail.module.css

@@ -136,7 +136,7 @@
   color: var(--text-muted);
 }
 
-/* Executions table */
+/* Exchanges table */
 .tableSection {
   background: var(--bg-surface);
   border: 1px solid var(--border-subtle);