feat(01-03): add test infrastructure, protocol version interceptor, and app bootstrap

- AbstractClickHouseIT base class with Testcontainers ClickHouse and schema init
- ProtocolVersionInterceptor validates X-Cameleer-Protocol-Version:1 on data/agent paths
- WebConfig registers interceptor with path patterns, excludes health/docs
- Cameleer3ServerApplication with @EnableScheduling and component scanning
- application-test.yml with small buffer config for tests

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/Cameleer3ServerApplication.java

@@ -0,0 +1,25 @@
+package com.cameleer3.server.app;
+
+import com.cameleer3.server.app.config.IngestionConfig;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.scheduling.annotation.EnableScheduling;
+
+/**
+ * Main entry point for the Cameleer3 Server application.
+ * <p>
+ * Scans {@code com.cameleer3.server.app} and {@code com.cameleer3.server.core} packages.
+ */
+@SpringBootApplication(scanBasePackages = {
+        "com.cameleer3.server.app",
+        "com.cameleer3.server.core"
+})
+@EnableScheduling
+@EnableConfigurationProperties(IngestionConfig.class)
+public class Cameleer3ServerApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Cameleer3ServerApplication.class, args);
+    }
+}