docs: redesign README (en/zh-CN/ja/ko) and add ESP32-S3 StopWatch firmware

[grpcer]

Summary

Two related pieces of work that round out the project for public consumption.

docs(readme): redesign the README + four-language localization

• Reworked the README into a proper landing page: hero with the web-console screenshot and a real-device photo, badges, an architecture diagram, and icon-marked sections.
• A Quick start that actually tells users how to view it — open the console at http://localhost:4717 (or tokpet open), with the GET /state feed one path over — plus Homebrew / npm / source install paths and a service-management table.
• Corrected the supported-provider list to what ships today: Claude and Codex (subscription) and DeepSeek (api-key balance). Everything else is clearly marked as planned (previously the table listed unimplemented vendors like Cursor as if available, and the status section was stale).
• Added full Simplified Chinese, Japanese, and Korean translations with a shared language switcher and localized anchors. Every sentence was reviewed by a native-language copy pass for accuracy and natural phrasing.

feat(firmware): bring the StopWatch firmware into the repo

• The ESP32-S3 desk-pet firmware now lives under firmware/: the M5Stack StopWatch board app (CO5300 466×466 round AMOLED over QSPI, CST820 touch, the I2C power/IO expander, two buttons), the LVGL "halo cat" UI, the board-agnostic shared/ components (state parsing, NVS config, Wi-Fi client with mDNS discovery and /state polling, SoftAP captive-portal provisioning, DNS responder), and the embedded captive-portal page.
• A comprehensive firmware/README.md covers the hardware, architecture, runtime data flow, and build/flash with ESP-IDF 5.5.
• All comments are English-only. Build output, fetched managed components, and the generated sdkconfig are git-ignored; firmware/ is excluded from the JS toolchain's Prettier pass.

Verification

• npm run typecheck && lint && format:check && test && build all pass (143 tests).
• README anchors verified against GitHub's slug algorithm (0 broken across all four languages); section headings unchanged by the copy passes.
• No CJK characters in any source or firmware file; localized READMEs are the only files that intentionally contain non-Latin text.

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