fix: increase ClickHouse pool size and reduce flush interval

Pool was hardcoded to 10 connections serving 7 concurrent write
streams + UI reads, causing "too many simultaneous queries" and
WriteBuffer overflow. Pool now defaults to 50 (configurable via
clickhouse.pool-size), flush interval reduced from 1000ms to 500ms.

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

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

@@ -39,7 +39,9 @@ public class ClickHouseConfig {
         ds.setJdbcUrl(props.getUrl());
         ds.setUsername(props.getUsername());
         ds.setPassword(props.getPassword());
-        ds.setMaximumPoolSize(10);
+        ds.setMaximumPoolSize(props.getPoolSize());
+        ds.setMinimumIdle(5);
+        ds.setConnectionTimeout(5000);
         ds.setPoolName("clickhouse-pool");
         return ds;
     }

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

@@ -8,6 +8,7 @@ public class ClickHouseProperties {
     private String url = "jdbc:clickhouse://localhost:8123/cameleer";
     private String username = "default";
     private String password = "";
+    private int poolSize = 50;
 
     public String getUrl() { return url; }
     public void setUrl(String url) { this.url = url; }
@@ -17,4 +18,7 @@ public class ClickHouseProperties {
 
     public String getPassword() { return password; }
     public void setPassword(String password) { this.password = password; }
+
+    public int getPoolSize() { return poolSize; }
+    public void setPoolSize(int poolSize) { this.poolSize = poolSize; }
 }

cameleer3-server-app/src/main/resources/application.yml

@@ -35,7 +35,7 @@ agent-registry:
 ingestion:
   buffer-capacity: 50000
   batch-size: 5000
-  flush-interval-ms: 1000
+  flush-interval-ms: 500
 
 cameleer:
   body-size-limit: ${CAMELEER_BODY_SIZE_LIMIT:16384}