refactor: move docker-compose files to deploy/ directory structure

Reorganize Docker configuration into environment-specific directories:
- deploy/dev/: Development with hot reload and source mounting
- deploy/test/: Ephemeral testing with branch isolation and dynamic ports
- deploy/prod/: Production with resource limits, logging, and restart policy

Key improvements in test compose:
- Dynamic ports (no fixed 3000/8484) for parallel test runs
- Branch-isolated container/network names via TEST_INSTANCE_ID
- service_healthy condition instead of service_started
- Increased retry counts for stability

deploy/test/docker-compose.yml

@@ -0,0 +1,48 @@
+# Test environment - ephemeral, branch-isolated
+services:
+  grist-mcp:
+    build:
+      context: ../..
+      dockerfile: Dockerfile
+    container_name: grist-mcp-test-${TEST_INSTANCE_ID:-default}
+    ports:
+      - "3000"  # Dynamic port
+    environment:
+      - CONFIG_PATH=/app/config.yaml
+      - GRIST_MCP_TOKEN=test-token
+      - PORT=3000
+    volumes:
+      - ../../tests/integration/config.test.yaml:/app/config.yaml:ro
+    depends_on:
+      mock-grist:
+        condition: service_healthy
+    networks:
+      - test-net
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:3000/health')"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+      start_period: 10s
+
+  mock-grist:
+    build:
+      context: ../../tests/integration/mock_grist
+    container_name: mock-grist-test-${TEST_INSTANCE_ID:-default}
+    ports:
+      - "8484"  # Dynamic port
+    environment:
+      - PORT=8484
+    networks:
+      - test-net
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8484/health')"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+      start_period: 10s
+
+networks:
+  test-net:
+    name: grist-mcp-test-${TEST_INSTANCE_ID:-default}
+    driver: bridge