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 -->

Cargo.toml

@@ -48,6 +48,7 @@ libc                   = "0.2"
 log                    = "0.4"
 loom                   = { version = "0.7", features = ["checkpoint"] }
 mimalloc               = "0.1"
+mp4parse               = "0.17"
 nanoid                 = "0.4"
 napi                   = { version = "3.0.0-beta.3", features = ["async", "chrono_date", "error_anyhow", "napi9", "serde"] }
 napi-build             = { version = "2" }