feat: add application log ingestion with OpenSearch storage

Agents can now send application log entries in batches via POST /api/v1/data/logs.
Logs are indexed directly into OpenSearch daily indices (logs-{yyyy-MM-dd}) using
the bulk API. Index template defines explicit mappings for full-text search readiness.

New DTOs (LogEntry, LogBatch) added to cameleer3-common in the agent repo.

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

cameleer3-server-core/src/main/java/com/cameleer3/server/core/logging/LogIndexService.java

@@ -0,0 +1,10 @@
+package com.cameleer3.server.core.logging;
+
+import com.cameleer3.common.model.LogEntry;
+
+import java.util.List;
+
+public interface LogIndexService {
+
+    void indexBatch(String agentId, String application, List<LogEntry> entries);
+}