feat(wfe-server): gRPC reflection, auto-generated schema endpoints, Dockerfile

- tonic-reflection for gRPC service discovery
  - /schema/workflow.json (JSON Schema from schemars derives)
  - /schema/workflow.yaml (same schema in YAML)
  - /schema/workflow.proto (raw proto file)
  - Multi-stage alpine Dockerfile with all executor features
  - Comprehensive configuration reference (wfe-server/README.md)
  - Release script (scripts/release.sh)
  - Bumped to 1.8.1

wfe-yaml/Cargo.toml

@@ -27,6 +27,7 @@ thiserror = { workspace = true }
 tracing = { workspace = true }
 chrono = { workspace = true }
 regex = { workspace = true }
+schemars = { version = "1", features = ["derive"] }
 deno_core = { workspace = true, optional = true }
 deno_error = { workspace = true, optional = true }
 url = { workspace = true, optional = true }