feat(clickhouse): add ClickHouseLogStore with LogIndex interface

Extract LogIndex interface from OpenSearchLogIndex. Both ClickHouseLogStore
and OpenSearchLogIndex implement it. Controllers now inject LogIndex.

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

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

@@ -0,0 +1,6 @@
+package com.cameleer3.server.core.storage;
+
+import java.time.Instant;
+
+public record LogEntryResult(String timestamp, String level, String loggerName,
+                             String message, String threadName, String stackTrace) {}

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

@@ -0,0 +1,15 @@
+package com.cameleer3.server.core.storage;
+
+import com.cameleer3.common.model.LogEntry;
+
+import java.time.Instant;
+import java.util.List;
+
+public interface LogIndex {
+
+    List<LogEntryResult> search(String application, String agentId, String level,
+                                String query, String exchangeId,
+                                Instant from, Instant to, int limit);
+
+    void indexBatch(String agentId, String application, List<LogEntry> entries);
+}