chore(server): improve transcript stability (#13821)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Enhanced audio/video detection for MP4 files to better distinguish
audio-only vs. video.

* **Dependencies**
* Added MP4 parsing dependency and updated AI provider libraries
(Anthropic, Google, OpenAI, etc.).

* **Bug Fixes**
  * Tightened authentication state validation for magic-link/OTP flows.
* Stricter space-join validation to reject invalid client
types/versions.
  * Improved transcript entry deduplication and data handling.

* **API**
* Transcript submit payload now requires infos and removes deprecated
url/mimeType fields.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/native/Cargo.toml

@@ -11,6 +11,7 @@ affine_common = { workspace = true, features = ["doc-loader"] }
 chrono        = { workspace = true }
 file-format   = { workspace = true }
 infer         = { workspace = true }
+mp4parse      = { workspace = true }
 napi          = { workspace = true, features = ["async"] }
 napi-derive   = { workspace = true }
 rand          = { workspace = true }