build(deps): bump @ai-sdk/openai-compatible from 2.0.27 to 2.0.28

Bumps [@ai-sdk/openai-compatible](https://github.com/vercel/ai) from 2.0.27 to 2.0.28.
- [Release notes](https://github.com/vercel/ai/releases)
- [Changelog](https://github.com/vercel/ai/blob/main/CHANGELOG.md)
- [Commits](https://github.com/vercel/ai/compare/@ai-sdk/openai-compatible@2.0.27...@ai-sdk/openai-compatible@2.0.28)

---
updated-dependencies:
- dependency-name: "@ai-sdk/openai-compatible"
  dependency-version: 2.0.28
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/backend/package.json

@@ -111,7 +111,7 @@
   },
   "dependencies": {
     "@ai-sdk/mcp": "^1.0.19",
-    "@ai-sdk/openai-compatible": "^2.0.27",
+    "@ai-sdk/openai-compatible": "^2.0.28",
     "@huggingface/gguf": "^0.3.3",
     "@huggingface/hub": "^2.8.1",
     "ai": "^6.0.78",