feat(report): add batch benchmarking, plot generation, and reproducible Docker environment

[cherninkiy]

Summary

This PR introduces several major improvements to the benchmarking workflow, reporting, and development environment:

• Batch benchmarking – a new bench_batch.c and batch mode in scripts/benchmark.sh to measure performance under batch processing.
• Plot generation & reports – scripts/plot_results.py aggregates sequential and batch CSV results, generates plots, and embeds them into docs/report.md. Figures are also copied to docs/figures/ for portability.
• Docker support – Dockerfile, docker_run helper, and install_deps.sh to provide a reproducible containerized build and benchmark environment with mounted results/docs.
• Cleanup – removed all references to the obsolete iaik_merkle_tree submodule, updated third_party orchestration and git message template accordingly.

Motivation

• Batch mode enables performance evaluation under realistic bulk‑operation scenarios.
• Automated plots and Markdown reports make it easier to analyse and share results.
• Docker ensures consistent dependencies across local development and CI.

Testing

# Run batch benchmark
./scripts/benchmark.sh --mode batch

# Generate plots and report
python3 scripts/plot_results.py

# Build and run inside Docker
./docker_run

Related

• Updates README with links to the new report.
• Portable PNG plots allow viewing without re‑running scripts.

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[gemini-code-assist]

Code Review

This pull request completes the MVP for the batch PQC benchmarking project by introducing a new batch signing benchmark, a comprehensive reporting and plotting pipeline, and Docker support for reproducible runs. Key changes include the removal of the external Merkle tree submodule and the addition of a detailed final report. Feedback focuses on addressing a potential integer overflow in memory allocation, resolving a conflict between Docker build steps and .dockerignore, improving constant definitions for hash sizes, and ensuring build isolation when using Docker volumes.