Add MaixCAM deployment helpers and localized static web UI

[SiYue-ZO]

Summary:

• Add a guided Docker toolchain setup script for Pulsar2 and TPU-MLIR images.
• Track conversion stages in job metadata and support cancelling active jobs.
• Ship a localized prebuilt static frontend with a startup helper so the web app can run without npm.
• Document venv setup, toolchain deployment, static frontend usage, and language switching.

Verification:

• bash -n scripts/setup_toolchains.sh start.sh
• python3 -m compileall convert_cli.py web/app.py converter