feat: log forwarding v2 — accept List<LogEntry>, add source field

Replace LogBatch wrapper with raw List<LogEntry> on the ingestion endpoint.
Add source column to ClickHouse logs table and propagate it through the
storage, search, and HTTP layers (LogSearchRequest, LogEntryResult,
LogEntryResponse, LogQueryController).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -13,6 +13,7 @@ import java.util.List;
  * @param exchangeId  Camel exchange ID filter
  * @param logger      logger name substring filter
  * @param environment optional environment filter (e.g. "dev", "staging", "prod")
+ * @param source      optional source filter: "app" or "agent"
  * @param from        inclusive start of time range (required)
  * @param to          inclusive end of time range (required)
  * @param cursor      ISO timestamp cursor for keyset pagination
@@ -27,6 +28,7 @@ public record LogSearchRequest(
         String exchangeId,
         String logger,
         String environment,
+        String source,
         Instant from,
         Instant to,
         String cursor,

cameleer3-server-core/src/main/java/com/cameleer3/server/core/storage/LogEntryResult.java

@@ -5,4 +5,4 @@ import java.util.Map;
 public record LogEntryResult(String timestamp, String level, String loggerName,
                              String message, String threadName, String stackTrace,
                              String exchangeId, String instanceId, String application,
-                             Map<String, String> mdc) {}
+                             Map<String, String> mdc, String source) {}