feat(providers): add SeekAi OpenAI-compatible New-API gateway

[HouMinXi]

Summary

SeekAi (https://seekai.cc) is a QuantumNous New-API gateway. Live GET /api/status on 2026-09-02 returned system_name=SeekAi, version=v1.0.0-rc.25, quota_display_type=USD. GET /v1/models is API-key gated (401 Invalid token with no key / dummy key).

This PR registers it as a thin OpenAI-compatible catalog entry, same shape as unorouter / anyapi / logfare:

• id seekai, alias ska
• https://seekai.cc/v1/chat/completions + live /v1/models via passthroughModels
• aggregator-list membership so New-API balance detection can opt in (newApiAggregatorBalance)
• no referral / aff query anywhere

Closes #11786

Test plan

DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx/esm --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit tests/unit/seekai-provider.test.ts tests/unit/provider-node-reserved-prefix.test.ts tests/unit/provider-translate-path-golden.test.ts

6 + reserved-prefix + golden pass. Also checked: drop authHint → catalog test fails; drop seekai from AGGREGATOR_PROVIDER_IDS → aggregator test fails. Restore from a working-tree backup, not git checkout (that would also drop uncommitted lines).

Live, no key:

curl -sS https://seekai.cc/api/status
# system_name=SeekAi, version=v1.0.0-rc.25
curl -sS https://seekai.cc/v1/models
# 401 Invalid token

POST /v1/chat/completions was not probed here (no key; the reporter's own chat call stalled).

Notes for reviewers

• apiHint is the OpenAI base (https://seekai.cc/v1). Registry baseUrl is the chat-completions URL, matching unorouter / anyapi / logfare.
• Other locale JSON files are not updated. Missing keys fall back to English via deepMergeFallback.
• Provider count docs (including AGENTS.md) say 356.

Not in this PR

• A dedicated executor / translator / DB migration
• Auto-enabling New-API balance (still opt-in via newApiAggregatorBalance)
• Hardcoded referral codes

[HouMinXi]

Rebased onto current release/v3.8.51 tip (2a6d45abe).

• old head 3cd86cd1d → new head eeb0db27b (GPG)
• range-diff: same SeekAi catalog patch; the only semantic delta vs the previous commit is taking upstream's locale-count drop (43 → 42, and dropping the retired docs/i18n/in/ locale) while keeping the provider-count bump (355 → 356)
• check-docs-counts-sync STRICT green; check-file-size --base-ref (CI PR mode) green; tests/unit/seekai-provider.test.ts + alias/prefix siblings 33/33

[HouMinXi]

Follow-up on the same commit (eeb0db27b → 499362bbb): CI unit shard 2/4 failed on tests/unit/i18n-pt-br.test.ts because providers.onboardingProviderDescriptions.seekai existed only in en.json.

Mirrored the key into the other 41 locale files (pt-BR translated to match the existing unorouter string; remaining locales use the English fallback, same as other catalog onboarding strings before they get a real translation). Did not fill unrelated missing keys (usage.kilo*). Local i18n-pt-br + seekai-provider 9/9.