feat(sync): bundle dictionary settings into the settings replica kind

[chrox]

Summary

Adds three entries to SETTINGS_WHITELIST so dictionary providerOrder, providerEnabled, and webSearches flow through the bundled settings replica with whole-field LWW. Collapses the original PR 6 (dict_provider_position) and PR 7 (dict_web_search) plans — per-element CRDT rows were over-engineered for settings users edit a few times a year, and the existing precedent (customHighlightColors, customThemes) is whole-field LWW too.

defaultProviderId (last-used tab) is deliberately excluded — that's per-device state.

What's in here

Commit 1 — bundle dictionary settings into the settings replica kind

• Three new whitelist entries for dictionarySettings.{providerOrder, providerEnabled, webSearches}
• customDictionaryStore.applyRemoteDictionarySettings mirrors pulled values into the in-memory store the reader popup + settings panel read from, so changes show up without a panel reload
• Fix: saveCustomDictionaries mutated the existing settings object in place and called setSettings with the same reference — the replicaSettingsSync subscriber's reference-equality check saw no change and never published. Build a fresh settings reference instead.

Commit 2 — make dict.id stable across devices (= contentId)

• dict.id used to equal the per-device random Math.random()-derived bundleDir, so two devices that imported the same .mdx had different ids for the same dictionary. The synced providerOrder was meaningless on the receiving side — providerOrder.filter((id) => known.has(id)) filtered every imported-dict entry out.
• id: bundleDir → id: contentId at the 4 import paths in dictionaryService.ts and in buildLocalDictFromRow. bundleDir keeps tracking the device-local on-disk path; on-disk layout is unchanged.
• After this change providerOrder / providerEnabled are uniformly contentId-keyed end-to-end, so the bundled settings replica syncs them across devices with no seam translation.

Test plan

• pnpm test — 4062 passed, 8 skipped
• pnpm lint — clean
• Two-browser end-to-end: reorder dictionaries on Device A → triggers replicas?kind=settings POST → Device B's next pull applies the same order
• Toggle a dict, add a custom web search, edit the URL: each triggers a settings replica push
• Fresh import: dict.id === contentId (verified via the 4-provider stardict / mdict / dict / slob import paths)

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