Implement dmrlet orchestrator for Docker Model Runner

- Add Cargo workspace with 8 crates
- dmrlet-core: Core types (Model, Worker, Endpoint, Config, Error, GPU)
- dmrlet-runtime: Process-based runtime for macOS/Windows
- dmrlet-scheduler: GPU-aware scheduler with placement logic
- dmrlet-network: Health checking, load balancing, service discovery
- dmrlet-store: Model cache with LRU eviction
- dmrlet-api: REST API server with Axum
- dmrlet-daemon: Main daemon binary (dmrletd)
- dmrlet-cli: CLI tool (dmrlet) with deploy, scale, delete, status commands
- Add proto file for future gRPC support
- Update .gitignore for Rust build artifacts

Co-authored-by: ericcurtin <1694275+ericcurtin@users.noreply.github.com>

Author: Copilot

.gitignore

@@ -12,3 +12,7 @@ llamacpp/build
 llamacpp/install
 
 .DS_Store
+
+# Rust build artifacts
+dmrlet/target/
+*.rs.bk