feat: replace custom memory MCP with Cognee remote server

- Remove memory_mcp.py (stdio markdown-file memory)
- Add Cognee MCP as remote Streamable HTTP toolset at 192.168.86.2:8003/mcp
- Filter to only remember/recall/forget tools via allowed_tools
- Update system prompt: Memory section moved to top priority with
  explicit 'call recall FIRST' instructions and examples
- Add COGNEE_MCP_URL env var to docker-compose
- Remove /memory volume mount (no longer needed)
- Rewrite memory tests to use Cognee HTTP client fixture
- 28/28 tests passing

docker-compose.yml

@@ -15,10 +15,10 @@ services:
       GEMMA_API_KEY: "${GEMMA_API_KEY:-not-needed}"
       WEB_MCP_ENABLED: "${WEB_MCP_ENABLED:-true}"
       FIRECRAWL_BASE: "${FIRECRAWL_BASE:-http://192.168.86.2:3002}"
+      COGNEE_MCP_URL: "${COGNEE_MCP_URL:-http://192.168.86.2:8003/mcp}"
     volumes:
       - ./livekit.yaml:/etc/livekit.yaml:ro
       - ./certs:/etc/voice/certs
-      - ./memory:/memory
       - ./skills:/skills
     healthcheck:
       test: ["CMD-SHELL", "curl -sk https://localhost:8090/ -o /dev/null && curl -s http://localhost:7880/ -o /dev/null"]