feat: add SSE transport and improve documentation

- Add Server-Sent Events (SSE) transport implementation with test coverage
- Add detailed documentation for both SSE and STDIO transports
- Extract common test logic into abstract base classes
- Add testcontainers support for SSE integration tests
- Replace System.out with SLF4J logging
- Externalize dependency versions to properties
- Implement endpoint event handling per MCP spec
- Add message endpoint sink for reliable message routing
- Improve error handling and graceful shutdown
- Update core module README with expanded features and examples
- Add dependency version properties and logging configuration
- Update architecture and class diagrams

Resolves #4

pom.xml

@@ -70,7 +70,12 @@
 		<assert4j.version>3.26.3</assert4j.version>
 		<junit.version>5.11.3</junit.version>
 		<mockito.version>5.11.0</mockito.version>
+		<testcontainers.version>1.20.4</testcontainers.version>
 
+		<slf4j-api.version>2.0.16</slf4j-api.version>
+		<logback.version>1.5.12</logback.version>
+		<jackson.version>2.18.2</jackson.version>
+		<springframework.version>6.1.13</springframework.version>
 
 		<!-- plugin versions -->
 		<maven-compiler-plugin.version>3.11.0</maven-compiler-plugin.version>
@@ -347,4 +352,4 @@
 		</repository>
 	</repositories>
 
-</project>
+</project>