Add Atlas Cloud provider catalog entry

[binyangzhu000-sudo]

Summary

• add Atlas Cloud to the provider catalog with an OpenAI-compatible configuration example
• include Atlas Cloud in Hermes config normalization with ATLASCLOUD_API_KEY support
• add focused coverage for Atlas Cloud default model and auth detection

Validation

• pnpm install --frozen-lockfile --ignore-scripts
• pnpm test src/server/hermes-config-migration.test.ts (4 passed)
• TypeScript syntax check for changed files
• git diff --check
• Atlas Cloud live /v1/models catalog check confirmed qwen/qwen3.5-flash and deepseek-ai/deepseek-v4-pro

Note: full pnpm install without --ignore-scripts hung in Electron postinstall locally. Full pnpm exec tsc --noEmit currently reports unrelated existing project-wide type errors outside this change.

No README changes. No sponsor, logo, credits, or partner promotion changes.