feat: add fastCRW web search provider

[us]

What

Adds fastCRW as a web search provider, alongside the existing Tavily / SerpApi / SearXNG / Ollama / Firecrawl options. Because Deep Research consumes the active web-search provider generically, this also makes fastCRW available for Deep Research with no extra wiring.

fastCRW is a SearXNG-based, Firecrawl-compatible search API. It can be used two ways:

• Managed cloud (https://api.fastcrw.com) with an API key from fastcrw.com.
• Self-hosted — point the Base URL at your own instance (e.g. http://localhost:3000) for unlimited, private search (no key required unless your instance enables auth).

Why a new provider instead of the existing Firecrawl entry

The Firecrawl entry is configKind: "none" (anonymous, no config). fastCRW needs a Bearer API key for the cloud and a configurable Base URL for self-hosting. Folding it into Firecrawl would change Firecrawl's behavior, so a sibling provider is cleaner and keeps existing providers untouched.

Changes (purely additive)

• stores/wiki-store.ts — "fastcrw" added to the SearchProvider union; fastCrwUrl? added to SearchProviderOverride.
• lib/web-search.ts — fastcrwSearch + normalizer + dispatch case + hasConfiguredSearchProvider/guard branches.
• components/settings/sections/web-search-section.tsx — provider entry with a new key+url config kind (renders both an API-key and a Base-URL input).
• i18n/en.json + i18n/zh.json — hint + error strings (parity preserved).
• lib/web-search.test.ts — 17 tests mirroring the Firecrawl suite.

Notes

• Endpoint is POST {baseUrl}/v1/search; results are read from either the cloud's flat data array or the self-hosted engine's data.results (both shapes handled).
• API key + Base URL are read only from the provider's own config (never a stale top-level key), so a keyless self-host never receives another provider's Authorization header.
• No README/docs edits (mirrors Firecrawl's footprint); intentionally no IP-block error string since fastCRW uses Bearer auth, not anonymous access.

Verification (local)

npm run typecheck · npx vitest run (1541 passed, incl. i18n parity) · npm run build — all green.