feat: add Avian as LLM provider

Add Avian (https://avian.io) as a new LLM provider with OpenAI-compatible
API support including chat completions, streaming, and function calling.

Models:
- deepseek/deepseek-v3.2 (164K context, $0.26/$0.38 per 1M tokens)
- moonshotai/kimi-k2.5 (131K context, $0.45/$2.20 per 1M tokens)
- z-ai/glm-5 (131K context, $0.30/$2.55 per 1M tokens)
- minimax/minimax-m2.5 (1M context, $0.30/$1.10 per 1M tokens)

Changes:
- Add AvianIcon to components/icons.tsx
- Add 'avian' to ProviderId type
- Add Avian provider definition with model pricing in models.ts
- Create providers/avian/ with index.ts and utils.ts
- Register provider in registry.ts and utils.ts

Author: avianion

apps/sim/components/icons.tsx

@@ -5024,6 +5024,23 @@ export function FirefliesIcon(props: SVGProps<SVGSVGElement>) {
   )
 }
 
+export const AvianIcon = (props: SVGProps<SVGSVGElement>) => (
+  <svg
+    {...props}
+    fill='currentColor'
+    height='1em'
+    viewBox='0 0 24 24'
+    width='1em'
+    xmlns='http://www.w3.org/2000/svg'
+  >
+    <title>Avian</title>
+    <path
+      d='M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm3.5 7.5L12 13l-3.5-3.5L12 6l3.5 3.5zM8 14.5l4 4 4-4H8z'
+      fill='#6366F1'
+    />
+  </svg>
+)
+
 export function BedrockIcon(props: SVGProps<SVGSVGElement>) {
   const id = useId()
   const gradientId = `bedrock_gradient_${id}`