fix(config): align rust-version to 1.91 matching clippy.toml msrv Refs #2770

Workspace.package declared 1.85; clippy.toml already has msrv = "1.91.0"
and the codebase uses Rust 1.91 APIs. Set to 1.91 for consistency.

Author: Test User

Cargo.toml

@@ -58,7 +58,7 @@ default-members = ["terraphim_server"]
 [workspace.package]
 version = "1.20.5"
 edition = "2024"
-rust-version = "1.85"
+rust-version = "1.91"
 authors = ["Terraphim Team <team@terraphim.ai>"]
 documentation = "https://terraphim.ai"
 homepage = "https://terraphim.ai"