feat(context): add Context model with admin-based ACL system

lib/models/context/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "hero-context"
+version.workspace = true
+edition.workspace = true
+description = "Context model for Hero platform"
+license = "MIT OR Apache-2.0"
+
+[dependencies]
+serde.workspace = true
+serde_json.workspace = true
+chrono.workspace = true
+rhai = { version = "1.19", features = ["sync"] }
+
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+uuid.workspace = true
+
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+uuid = { workspace = true, features = ["js"] }