v2.0.0 — Modular rewrite with esbuild, full test suite

[rookieInTraining]

Refactor to modular ES module architecture for v2.0.0

• Split monolithic devtools.js into 8 UI modules (js/ui/)
• Split monolithic service-worker.js into 7 SW modules (js/sw/)
• Replace Terser build with esbuild for ~100x faster bundling
• Add Jest unit tests for devtools panel and service worker
• Add Playwright e2e test scaffolding
• Add ESLint + Prettier for consistent code style
• Add GitHub Actions workflows for CI and release automation
• Add version sync, packaging scripts, and npm release workflow
• Add CONTRIBUTING.md and Chrome Web Store assets
• Fix base64 encoding overflow on large payloads (>65KB)
• Correct license field to Apache-2.0