feat: markdown memory system — Hope learns from conversations

- agent/memory_mcp.py: MCP server with memory_recall, memory_save, memory_list
  tools backed by .md files in /memory (simple keyword matching for v1)
- memory/ dir bind-mounted into container, persists across rebuilds,
  easily backed up via git
- System prompt instructs Hope to recall on past references and save
  personal info/preferences naturally without announcing it
- Dockerfile: copy memory_mcp.py; compose: ./memory:/memory volume

docker-compose.yml

@@ -18,6 +18,7 @@ services:
     volumes:
       - ./livekit.yaml:/etc/livekit.yaml:ro
       - ./certs:/etc/voice/certs
+      - ./memory:/memory
     healthcheck:
       test: ["CMD-SHELL", "curl -sk https://localhost:8090/ -o /dev/null && curl -s http://localhost:7880/ -o /dev/null"]
       interval: 15s