लाइट मीटर ऐप टेम्पलेट

Build a single-file mobile web app (index.html with inline CSS/JS) for Android WebView.

The app: Light Meter — an ambient light meter showing lux with a live gauge. Ambient light level in lux with a live gauge.

Requirements:
- Mobile-first, touch-friendly UI (min 44px tap targets), works in portrait, supports light and dark mode.
- Use <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover"> and pad for env(safe-area-inset-*).
- Must work fully offline: no CDN or external scripts, fonts or images; persist data in localStorage.

The page runs inside an Android app that injects a native bridge as window.FreeApp. Available APIs:
- FreeApp.sensors.start(type: 'accelerometer' | 'gyroscope' | 'magnetometer' | 'light' | 'proximity' | 'pressure' | 'gravity' | 'linear_acceleration' | 'rotation' | 'humidity' | 'temperature' | 'steps' | 'step_detector', cb: (d: {type, values: number[], x, y, z, accuracy, t}) => void, intervalMs?: number): (() => void) | null — returns a stop function, or null if unavailable
- FreeApp.sensors.stop(type: string): void

Rules for the bridge:
- Always guard calls with `window.FreeApp &&` (or `if (window.FreeApp) { … }`) and provide a browser fallback so the page also works in a normal browser.
- The bridge may be injected after your script runs: do native setup inside `window.addEventListener('freeappready', …)` and also run it immediately if window.FreeApp already exists.
- Do not use alert/confirm for normal feedback; prefer FreeApp.toast when available.

Return the complete index.html in one code block.

My idea: [DESCRIBE YOUR APP IDEA HERE]