feat: add ClickHouse schema initializer with agent_metrics DDL

Adds ClickHouseSchemaInitializer that runs on ApplicationReadyEvent,
scanning classpath:clickhouse/*.sql in filename order and executing each
statement. Adds V1__agent_metrics.sql with MergeTree table, tenant/agent
partitioning, and 365-day TTL.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/ClickHouseSchemaInitializer.java

@@ -0,0 +1,52 @@
+package com.cameleer3.server.app.config;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.Comparator;
+
+@Component
+@ConditionalOnProperty(name = "clickhouse.enabled", havingValue = "true")
+public class ClickHouseSchemaInitializer {
+
+    private static final Logger log = LoggerFactory.getLogger(ClickHouseSchemaInitializer.class);
+
+    private final JdbcTemplate clickHouseJdbc;
+
+    public ClickHouseSchemaInitializer(
+            @Qualifier("clickHouseJdbcTemplate") JdbcTemplate clickHouseJdbc) {
+        this.clickHouseJdbc = clickHouseJdbc;
+    }
+
+    @EventListener(ApplicationReadyEvent.class)
+    public void initializeSchema() throws IOException {
+        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
+        Resource[] scripts = resolver.getResources("classpath:clickhouse/*.sql");
+
+        Arrays.sort(scripts, Comparator.comparing(Resource::getFilename));
+
+        for (Resource script : scripts) {
+            String sql = script.getContentAsString(StandardCharsets.UTF_8);
+            log.info("Executing ClickHouse schema script: {}", script.getFilename());
+            for (String statement : sql.split(";")) {
+                String trimmed = statement.trim();
+                if (!trimmed.isEmpty()) {
+                    clickHouseJdbc.execute(trimmed);
+                }
+            }
+        }
+
+        log.info("ClickHouse schema initialization complete ({} scripts)", scripts.length);
+    }
+}

cameleer3-server-app/src/main/resources/clickhouse/V1__agent_metrics.sql

@@ -0,0 +1,14 @@
+CREATE TABLE IF NOT EXISTS agent_metrics (
+    tenant_id          LowCardinality(String) DEFAULT 'default',
+    collected_at       DateTime64(3),
+    agent_id           LowCardinality(String),
+    metric_name        LowCardinality(String),
+    metric_value       Float64,
+    tags               Map(String, String) DEFAULT map(),
+    server_received_at DateTime64(3) DEFAULT now64(3)
+)
+ENGINE = MergeTree()
+PARTITION BY (tenant_id, toYYYYMM(collected_at))
+ORDER BY (tenant_id, agent_id, metric_name, collected_at)
+TTL collected_at + INTERVAL 365 DAY DELETE
+SETTINGS index_granularity = 8192;