build(deps): bump ai from 4.3.18 to 4.3.19

Bumps [ai](https://github.com/vercel/ai) from 4.3.18 to 4.3.19.
- [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/[email protected]@4.3.19)

---
updated-dependencies:
- dependency-name: ai
  dependency-version: 4.3.19
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

packages/backend/package.json

@@ -113,7 +113,7 @@
     "@ai-sdk/openai-compatible": "^0.2.14",
     "@huggingface/gguf": "^0.1.17",
     "@huggingface/hub": "^2.4.0",
-    "ai": "^4.3.18",
+    "ai": "^4.3.19",
     "express": "^4.21.2",
     "express-openapi-validator": "^5.5.7",
     "isomorphic-git": "^1.32.0",