chore: bump rust-version to 1.93 across workspace

Aligns ladybug-rs and ladybug-contract MSRV to Rust 1.93 target,
matching n8n-rs (already compliant). Part of constellation-wide MSRV
alignment.

https://claude.ai/code/session_016HQG2eoyNAwML6WP8WhbAG

Author: claude

Cargo.toml

@@ -5,7 +5,7 @@ members = [".", "crates/ladybug-contract"]
 name = "ladybug"
 version = "0.3.0"
 edition = "2024"
-rust-version = "1.88"
+rust-version = "1.93"
 license = "Apache-2.0"
 description = "Crystal Lake: Unified Cognitive Database with 4096 CAM Operations, Quantum-Inspired Operators, and 144 Verb Graph Substrate"
 repository = "https://github.com/AdaWorldAPI/ladybug-rs"

crates/ladybug-contract/Cargo.toml

@@ -2,7 +2,7 @@
 name = "ladybug-contract"
 version = "0.1.0"
 edition = "2024"
-rust-version = "1.88"
+rust-version = "1.93"
 license = "Apache-2.0"
 description = "Substrate types for LadybugDB: Container, CogRecord, CAM codebook, CognitiveAddress"
 repository = "https://github.com/AdaWorldAPI/ladybug-rs"