Add Atlas Cloud API provider

[binyangzhu000-sudo]

Summary

• Add atlascloud_api as an OpenAI-compatible API provider in the key-vault registry and provider config.
• Wire Atlas Cloud into validation, token format checks, quota handling, environment export, CLI compatibility, and frontend provider schemas/lists.
• Use ATLASCLOUD_API_KEY, optional ATLASCLOUD_API_BASE, and the default base URL https://api.atlascloud.ai/v1.

Validation

• cargo test --manifest-path src-tauri/Cargo.toml -p key_vault provider_config --no-fail-fast (22 passed)
• cargo test --manifest-path src-tauri/Cargo.toml -p key_vault validate --no-fail-fast (29 passed)
• cargo test --manifest-path src-tauri/Cargo.toml -p key_vault model_type --no-fail-fast (11 passed)
• cargo test --manifest-path src-tauri/Cargo.toml -p key_vault compatibility_comes_from_the_central_cli_registry --no-fail-fast (1 passed)
• ./node_modules/.bin/eslint src/api/tauri/rpc/schemas/validation.ts src/components/ModelIcon/config.ts src/assets/providers/index.ts
• git diff --cached --check
• Atlas Cloud live model catalog confirmed qwen/qwen3.5-flash and deepseek-ai/deepseek-v4-pro.

Notes:

• Full tsc --noEmit currently fails in pre-existing ProjectManager virtualized list typing tests unrelated to this provider change.
• Full cargo fmt --manifest-path src-tauri/Cargo.toml --all --check reports existing formatting drift outside this change; this PR keeps the diff scoped to Atlas Cloud provider files.

No README/docs/logo/sponsor/credits/partner promotional changes were added.

[Harry19081]

hi @binyangzhu000-sudo Thank you for the PR. For new providers, we need a SVG of the provider. Please provide one.