Add Episodic Memory Strategy Tutorial

## Description
Add tutorial demonstrating **Episodic Memory Strategy** for AgentCore Memory.

## Why Needed
Repository has tutorials for semantic/summary/preference strategies but no episodic memory sample - a key differentiator.

## Proposed Solution
Add tutorial at `01-tutorials/04-AgentCore-memory/06-episodic-strategy/` with:
- **Use Case**: Code Debugging Assistant
- **Framework**: Strands Agents with memory hooks
- **Features**: Episode detection, reflection generation, learning from past interactions

## Deliverables
- README.md with architecture diagram
- code-assistant.ipynb with implementation
- architecture.png diagram
- requirements.txt