feat: add Avian as a new API provider

[avianion]

Summary

• Adds Avian as a new OpenAI-compatible LLM API provider
• Follows the BaseOpenAiCompatibleProvider pattern (same as SambaNova, Fireworks)
• Includes 4 models with competitive pricing via the AVIAN_API_KEY environment variable

Models

Model	Context	Max Output	Input Price	Output Price
deepseek/deepseek-v3.2 (default)	164K	65K	$0.26/M	$0.38/M
moonshotai/kimi-k2.5	131K	8K	$0.45/M	$2.20/M
z-ai/glm-5	131K	16K	$0.30/M	$2.55/M
minimax/minimax-m2.5	1M	1M	$0.30/M	$1.10/M

Changes

New files:

• packages/types/src/providers/avian.ts — model type definitions and pricing
• src/api/providers/avian.ts — handler extending BaseOpenAiCompatibleProvider
• src/api/providers/__tests__/avian.spec.ts — 17 unit tests
• webview-ui/src/components/settings/providers/Avian.tsx — settings UI

Modified files (provider registration):

• packages/types/src/providers/index.ts — export types + default model
• packages/types/src/provider-settings.ts — schema, provider name, model ID key, MODELS_BY_PROVIDER
• src/api/providers/index.ts — export handler
• src/api/index.ts — factory switch case
• src/shared/ProfileValidator.ts — profile model ID resolution
• webview-ui/src/components/settings/providers/index.ts — export UI component
• webview-ui/src/components/settings/constants.ts — MODELS_BY_PROVIDER + PROVIDERS list
• webview-ui/src/components/settings/utils/providerModelConfig.ts — service config + defaults
• webview-ui/src/components/settings/ApiOptions.tsx — provider rendering + model config
• webview-ui/src/components/ui/hooks/useSelectedModel.ts — model selection case
• webview-ui/src/i18n/locales/en/settings.json — English translations

Test plan

• All 17 new unit tests pass (npx vitest run src/api/providers/__tests__/avian.spec.ts)
• TypeScript type checks pass across all 14 packages (turbo check-types)
• ESLint passes across all 14 packages with zero warnings (turbo lint)
• Prettier formatting validated via pre-commit hook
• All 146 existing types package tests still pass
• ProfileValidator and constants tests pass without regression
• Manual testing: select Avian provider in settings, enter API key, verify model picker shows all 4 models
• Manual testing: send a message using DeepSeek V3.2 via Avian and verify streaming response

Interactively review PR in Roo Code Cloud