[User Story] - Add support for Langchain4j Agentic Module

**Description**
Convert the supervisor, account, transaction, payment agents to use the recently released agentic module from langchain4j

**Current Behavior**
The current agentic implementation is based on a custom react agent based on langchain4j low level API.

**Acceptance Criteria**

- [ ] No regression on account, transaction, payment flows.

**Design Considerations**
- Consider to use the pre-built supervisor orchestration. https://docs.langchain4j.dev/tutorials/agents#pure-agentic-ai.

**Main Affected Modules and/or Classes**
-https://github.com/Azure-Samples/agent-openai-java-banking-assistant/blob/main/app/copilot/langchain4j-agents/src/main/java/com/microsoft/openai/samples/assistant/langchain4j/agent/SupervisorAgent.java
- https://github.com/Azure-Samples/agent-openai-java-banking-assistant/blob/main/app/copilot/langchain4j-agents/src/main/java/com/microsoft/openai/samples/assistant/langchain4j/agent/mcp/AccountMCPAgent.java
- https://github.com/Azure-Samples/agent-openai-java-banking-assistant/blob/main/app/copilot/langchain4j-agents/src/main/java/com/microsoft/openai/samples/assistant/langchain4j/agent/mcp/PaymentMCPAgent.java
- https://github.com/Azure-Samples/agent-openai-java-banking-assistant/blob/main/app/copilot/langchain4j-agents/src/main/java/com/microsoft/openai/samples/assistant/langchain4j/agent/mcp/TransactionHistoryMCPAgent.java

**References**
[Link to docs, ADRs, samples, related issues. Example:
- Agent middleware docs:
- Sample middleware implementation: ](https://docs.langchain4j.dev/tutorials/agents)

Beginne mit SupervisorAgent.java sowie den in diesem Issue aufgeführten Klassen AccountMCPAgent.java, PaymentMCPAgent.java und TransactionHistoryMCPAgent.java und lies anschließend die verlinkte Dokumentation zum agentic-Modul von LangChain4j. Migriere den Supervisor und die drei Agents zum veröffentlichten Modul und stelle sicher, dass die Account-, Transaktions- und Payment-Flows keine Regressionen aufweisen.

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