fix(docker): add procps to Dockerfile.cursor for pgrep healthcheck

HEALTHCHECK uses `pgrep -x openab`, which requires procps. Debian
slim does not ship with it, so the healthcheck was silently failing
(command not found) and the pod would enter Unhealthy state.

Same fix pattern as pending PR #234 for the other Dockerfiles.
Addresses review comment on PR #301 from @masami-agent.

Author: brettchien

Dockerfile.cursor

@@ -8,7 +8,7 @@ RUN touch src/main.rs && cargo build --release
 
 # --- Runtime stage ---
 FROM debian:bookworm-slim
-RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates curl && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates curl procps && rm -rf /var/lib/apt/lists/*
 
 # Install Cursor Agent CLI (pinned version)
 ARG CURSOR_VERSION=2026.04.08-a41fba1