[Feature] Server-side multi-provider/model support (#583)

* [Feature] Server side multi-pvorider/model support

* copilot suggesition implemented

* feat: improve model selector UI and auto-select default server model

- Replace emoji headers with Lucide icons (Monitor, User)
- Fix transition-all to explicit properties per web guidelines
- Use CSS padding instead of hardcoded space indentation
- Add ModelSelectorSectionHeader component for section headers
- Replace Star icon with "default" text label
- Style Configure button with muted text color
- Auto-select default server model when page loads
- Support AI_MODELS_CONFIG env var for cloud deployments
- Support custom apiKeyEnv/baseUrlEnv per provider config

* docs: update server-side multi-model configuration documentation

- Add AI_MODELS_CONFIG env var option for cloud deployments
- Document apiKeyEnv and baseUrlEnv fields for custom env var names
- Document default field for auto-selecting default model
- Remove deprecated version field from examples
- Add field reference table for clarity

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Co-authored-by: dayuan.jiang <jdy.toh@gmail.com>

package.json

@@ -37,7 +37,7 @@
         "@ai-sdk/deepseek": "^2.0.0",
         "@ai-sdk/gateway": "^3.0.0",
         "@ai-sdk/google": "^3.0.0",
-        "@ai-sdk/google-vertex": "^4.0.11",
+        "@ai-sdk/google-vertex": "^4.0.16",
         "@ai-sdk/openai": "^3.0.0",
         "@ai-sdk/react": "^3.0.1",
         "@aws-sdk/client-dynamodb": "^3.957.0",