feat: add system theme option with an accessible theme menu

[justraman]

Closes #112

After first use the theme toggle became a binary light/dark switch and
stopped following OS theme changes. This replaces the cycling button
with a small popover menu offering Light / Dark / System, where System
tracks prefers-color-scheme live.

[github-actions]

⚡ Performance Report

⚠️ No baseline found on main. This PR's results are recorded but cannot be compared.
Merge to main to establish a baseline.

[github-actions]

Bundle Size Report

Chunks over 500 KB:

File	Raw	Brotli	Gzip
host/assets/paseo.smol-DboPaEh1.json	1.84 MB	941.7 KB	1019.4 KB
host/assets/paseo-people-next.smol.json	3.36 MB	1.68 MB	1.82 MB
host/assets/smoldot.js	2.98 MB	2.22 MB (+2 B)	2.23 MB (+1 B)
host/assets/smoldot_worker.js	2.95 MB	2.21 MB	2.22 MB
host/assets/wasm/web/truapi_server_bg.wasm	2.01 MB	627.5 KB	830.0 KB
Total	14.31 MB (+13.3 KB)	7.98 MB (+2.3 KB) (-44%)	8.46 MB (+2.6 KB)

All files

File	Raw	Brotli	Gzip
host/.well-known/apple-app-site-association	738 B	738 B	738 B
host/.well-known/assetlinks.json	1.3 KB	317 B	391 B
host/assets/bridge.js	69.0 KB	18.9 KB (-1 B)	21.7 KB (-1 B)
host/assets/browser.js	22.9 KB	7.6 KB (+24 B)	8.6 KB
host/assets/client.js	100.1 KB	29.4 KB (+64 B)	32.4 KB (+2 B)
host/assets/dist.js	39.0 KB	12.8 KB (-68 B)	14.6 KB
host/assets/dotli-debug-bus.js	710 B	710 B	710 B
host/assets/get-sync-provider.js	2.8 KB	1.1 KB	1.2 KB (+2 B)
host/assets/hex.js	154 B	154 B	154 B
host/assets/index.js	191.8 KB (+1.6 KB)	47.9 KB (+295 B)	57.3 KB (+389 B)
host/assets/index.css	47.1 KB (+725 B)	7.4 KB (+94 B)	8.2 KB (+111 B)
host/assets/manifest.js	22.5 KB	7.3 KB (-3 B)	8.0 KB (+1 B)
host/assets/panel.js	76.2 KB	20.6 KB (+9 B)	23.2 KB (-3 B)
host/assets/paseo.smol-DboPaEh1.json	1.84 MB	941.7 KB	1019.4 KB
host/assets/paseo-people-next.smol.json	3.36 MB	1.68 MB	1.82 MB
host/assets/paseo.smol.json	22.3 KB	5.1 KB	5.9 KB
host/assets/previewnet.smol.json	179.0 KB	13.8 KB	34.0 KB
host/assets/resolve.js	156 B	156 B	156 B
host/assets/rpc-resolve.js	2.4 KB	1.0 KB (+13 B)	1.2 KB (-1 B)
host/assets/smoldot.js	2.98 MB	2.22 MB (+2 B)	2.23 MB (+1 B)
host/assets/smoldot_worker.js	2.95 MB	2.21 MB	2.22 MB
host/assets/spans.js	2.6 KB	1.1 KB	1.3 KB
host/assets/src.js	1.8 KB	848 B (-12 B)	945 B (+1 B)
host/assets/styles.css	15.3 KB	3.3 KB	3.8 KB
host/assets/wasm/web/README.md	11.5 KB	11.5 KB	11.5 KB
host/assets/wasm/web/package.json	371 B	371 B	371 B
host/assets/wasm/web/truapi_server.d.ts	6.9 KB	6.9 KB	6.9 KB
host/assets/wasm/web/truapi_server.js	35.6 KB	6.2 KB	7.2 KB
host/assets/wasm/web/truapi_server_bg.wasm	2.01 MB	627.5 KB	830.0 KB
host/assets/wasm/web/truapi_server_bg.wasm.d.ts	2.5 KB	2.5 KB	2.5 KB
host/assets/web.js	13.2 KB	3.5 KB (+2 B)	4.0 KB (+2 B)
host/assets/worker-runtime.js	6.3 KB (+6.2 KB)	1.6 KB (+1.5 KB)	1.8 KB (+1.7 KB)
host/assets/worker-runtime.js	106 B	106 B	106 B
host/assets/ws.js	23.1 KB	7.5 KB	8.2 KB (+3 B)
host/dotli.png	11.5 KB	11.5 KB	11.5 KB
host/favicon.svg	1.8 KB	1.8 KB	1.8 KB
host/host-sw.js	2.7 KB	1.1 KB (+11 B)	1.2 KB (+2 B)
host/icon-192.png	12.5 KB	12.5 KB	12.5 KB
host/icon-512.png	42.8 KB	42.8 KB	42.8 KB
host/index.html	24.0 KB (+4.0 KB)	4.6 KB (+232 B)	5.7 KB (+274 B)
host/manifest.webmanifest	441 B	441 B	441 B
host/workbox.js	14.8 KB	4.6 KB	5.1 KB
sandbox/app-sw.js	9.6 KB	3.1 KB (+7 B)	3.5 KB (+2 B)
sandbox/assets/bitswap-bridge.js	840 B	840 B	840 B
sandbox/assets/fetch.js	3.4 KB	1.2 KB (-1 B)	1.4 KB (-2 B)
sandbox/assets/index.js	118.0 KB	33.7 KB (+72 B)	39.6 KB (+3 B)
sandbox/assets/index.css	47.1 KB (+725 B)	7.4 KB (+94 B)	8.2 KB (+111 B)
sandbox/favicon.svg	1.8 KB	1.8 KB	1.8 KB
sandbox/index.html	1.7 KB	582 B (+1 B)	786 B
Total	14.31 MB (+13.3 KB)	7.98 MB (+2.3 KB) (-44%)	8.46 MB (+2.6 KB)

_{Commit: 584192b}

[BigTava]

No inline commets in tests. Pure // Given // When // Then please, so it easier for humans to see

[github-actions]

⚠️ E2E Product suite skipped — Nova signing bot is unavailable.

This is a Nova-side outage and not a dot.li test failure. Re-run
from the Actions tab once the bot recovers.

Logs: https://github.com/paritytech/dotli-community/actions/runs/30840005908

[leonardocustodio]

lgtm

[github-actions]

❌ E2E Product suite failed on b483090c72f276ead7fb6baf2468a50514159207 — 38 passed, 7 failed, 17 skipped.

Failed tests:

• Get Product Account
• Product Signer
• Product Account Alias
• Bulletin Allowance
• All Allowances
• Query Balance
• Sign Raw Message

Logs: https://github.com/paritytech/dotli-community/actions/runs/31338674605
Artifacts: e2e-product-results (uploaded above) — open the failed test's trace.zip with npx playwright show-trace.