feat: add Atlas Cloud as an OpenAI-compatible provider

[lucaszhu-hue]

What

Adds Atlas Cloud as a new built-in model provider. Atlas Cloud (https://atlascloud.ai) is an OpenAI-compatible gateway exposing many open and proprietary LLMs through a single endpoint (https://api.atlascloud.ai/v1).

How

Atlas Cloud speaks the standard OpenAI /v1/chat/completions (and /v1/models) API, so the integration mirrors the existing 302.AI provider 1:1 — another OpenAI-compatible gateway already in the project. No new request/response handling was needed.

Touched the same set of integration points as 302.AI:

• app/client/platforms/atlascloud.ts — new platform client (AtlasCloudApi), streaming + tool-calls + reasoning, modeled on ai302.ts
• app/api/atlascloud.ts — new server proxy route, modeled on 302ai.ts
• app/api/[provider]/[...path]/route.ts — dispatch the new ApiPath.AtlasCloud
• app/constant.ts — ATLASCLOUD_BASE_URL, ServiceProvider.AtlasCloud, ModelProvider.AtlasCloud, ApiPath.AtlasCloud, AtlasCloud config object, default model list, and DEFAULT_MODELS entry
• app/client/api.ts — client dispatch + auth-header/key resolution branch
• app/config/server.ts — ATLASCLOUD_URL / ATLASCLOUD_API_KEY env support
• app/api/auth.ts — inject the Atlas Cloud server key for this provider
• app/store/access.ts — default URL, store fields, validator
• app/components/settings.tsx — provider config UI (endpoint + API key)
• app/locales/en.ts, app/locales/cn.ts — settings strings

Configuration

Server-side env vars (same pattern as other providers):

ATLASCLOUD_API_KEY=your-atlas-cloud-key
ATLASCLOUD_URL=https://api.atlascloud.ai   # optional, defaults to this

Users can also enter their own key in Settings → Custom Endpoint → Atlas Cloud.

Testing

• npx tsc --noEmit passes with 0 errors
• Code formatted with the project's Prettier config
• The new provider appears automatically in the settings dropdown (it is generated from the ServiceProvider enum)

Questions can go to marketing@atlascloud.ai.