Enhancement: Newer Dart Runtime (upgrade from 3.5.2)

### 🔖 Enhancement description I would like to request that Appwrite upgrade their Dart runtime. Currently the newest we can use is 3.5.2 labelled as "Dart 3.5". The 1.8 release of the self-hosted Appwrite has Dart 3.8. Dart 3.10 was release on November 12, 2025. ### 🎤 Pitch We should update the runtime because we shouldn't be forced to write new legacy code. We can't use the latest major versions libraries for OpenAI or Postgres for example. ### 👀 Have you spent some time to check if this issue has been raised before? - [x] I checked and didn't find similar issue ### 🏢 Have you read the Code of Conduct? - [x] I have read the [Code of Conduct](https://github.com/appwrite/.github/blob/main/CODE_OF_CONDUCT.md)