fix: filter exchanges by application and restore snake_case sort columns

Add application_name filter to OpenSearch query builder — sidebar
app selection now correctly filters the exchange list. The
application field was being resolved to agentIds in the controller
but never applied as a query filter in OpenSearch.

Also restore snake_case sort column mapping since the OpenSearch
toMap() serializer uses snake_case field names (start_time, route_id,
etc.), not camelCase.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/search/OpenSearchIndex.java

@@ -166,6 +166,8 @@ public class OpenSearchIndex implements SearchIndex {
             filter.add(termQuery("agent_id.keyword", request.agentId()));
         if (request.correlationId() != null)
             filter.add(termQuery("correlation_id.keyword", request.correlationId()));
+        if (request.application() != null && !request.application().isBlank())
+            filter.add(termQuery("application_name.keyword", request.application()));
 
         // Full-text search across all fields + nested processor fields
         if (request.text() != null && !request.text().isBlank()) {

cameleer3-server-core/src/main/java/com/cameleer3/server/core/search/SearchRequest.java

@@ -59,6 +59,18 @@ public record SearchRequest(
             "durationMs", "executionId", "applicationName"
     );
 
+    /** Maps camelCase API sort field names to snake_case OpenSearch/DB column names. */
+    private static final java.util.Map<String, String> SORT_FIELD_TO_COLUMN = java.util.Map.ofEntries(
+            java.util.Map.entry("startTime", "start_time"),
+            java.util.Map.entry("status", "status"),
+            java.util.Map.entry("agentId", "agent_id"),
+            java.util.Map.entry("routeId", "route_id"),
+            java.util.Map.entry("correlationId", "correlation_id"),
+            java.util.Map.entry("durationMs", "duration_ms"),
+            java.util.Map.entry("executionId", "execution_id"),
+            java.util.Map.entry("applicationName", "application_name")
+    );
+
     public SearchRequest {
         if (limit <= 0) limit = DEFAULT_LIMIT;
         if (limit > MAX_LIMIT) limit = MAX_LIMIT;
@@ -67,12 +79,9 @@ public record SearchRequest(
         if (!"asc".equalsIgnoreCase(sortDir)) sortDir = "desc";
     }
 
-    /**
+    /** Returns the snake_case column name for OpenSearch/DB ORDER BY. */
-     * Returns the validated sort field name for OpenSearch ORDER BY.
-     * Field names match the ExecutionDocument record fields (camelCase).
-     */
     public String sortColumn() {
-        return sortField;
+        return SORT_FIELD_TO_COLUMN.getOrDefault(sortField, "start_time");
     }
 
     /** Create a copy with resolved agentIds (from application name lookup). */