feat(server): converge legacy compatibility (#15426)

#### PR Dependency Tree


* **PR #15426** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

* **New Features**
* Added workspace BYOK profiles with provider/model catalogs, capability
validation, connection probing, credential rotation, reordering, and
secure local leases.
* Added Copilot route options, selectable targets, managed tiers,
explicit profile/model overrides, and improved streaming with tool
callbacks and abort support.
* Added Copilot availability controls to prevent access when the feature
is disabled.
* **Changes**
* Simplified Copilot configuration and removed legacy provider-specific
settings.
* Removed obsolete model, token-cost, transcript strategy, and provider
metadata fields from public responses.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/native/Cargo.toml

@@ -20,7 +20,9 @@ chrono = { workspace = true }
 crc32fast = "1.5.0"
 doc_extractor = { workspace = true }
 file-format = { workspace = true }
+gcp_auth = "0.12.7"
 hex = { workspace = true }
+hkdf = { workspace = true }
 hmac = "0.13"
 homedir = { workspace = true }
 image = { workspace = true }
@@ -62,7 +64,12 @@ sqlx = { workspace = true, default-features = false, features = [
 ] }
 thiserror.workspace = true
 tiktoken-rs = { workspace = true }
-tokio = { workspace = true, features = ["rt-multi-thread", "sync", "time"] }
+tokio = { workspace = true, features = [
+  "net",
+  "rt-multi-thread",
+  "sync",
+  "time",
+] }
 unicode-normalization = "0.1"
 unicode_skeleton = "0.1.1"
 url = { workspace = true }
@@ -70,6 +77,7 @@ uuid = { workspace = true, features = ["v4"] }
 v_htmlescape = { workspace = true }
 webpki-roots = "1.0"
 y-octo = { workspace = true, features = ["large_refs"] }
+zeroize = { workspace = true }
 
 [target.'cfg(not(target_os = "linux"))'.dependencies]
 mimalloc = { workspace = true }