feat: add GPT-5.5 and DeepSeek V4 Pro cloud models

[fengju0213]

Summary

Closes #1583.

Adds GPT-5.5 and DeepSeek V4 Pro as cloud model options in the desktop model selector.

Changes

• Add gpt-5.5 and deepseek-v4-pro to the cloud model type whitelist.
• Add both models to the Agents > Models cloud selector and default model menu.
• Add localized display names for all supported setting locale files.
• Replace the cloud platform fallback logic with an explicit model-to-platform map:
  • GPT models -> azure
  • Claude models -> aws-bedrock-converse
  • Gemini models -> gemini
  • DeepSeek V4 Pro -> deepseek
  • Minimax M2.5 -> minimax
• Add unit coverage for cloud model platform mapping.

Validation

• npx vitest run test/unit/store/chatStore.test.ts
• npx eslint src/store/authStore.ts src/store/chatStore.ts test/unit/store/chatStore.test.ts --no-warn-ignored
• npm run type-check