rename crates/ to engrams/, bindings/ to receptors/

- crates/ → engrams/ (Rust engrams live here)
- bindings/ → receptors/ (cross-language access points into the graph)
- Cargo.toml workspace paths updated

engram/engrams/engram-ffi/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "engram-ffi"
+version = "0.1.0"
+edition = "2021"
+description = "C FFI bindings for engram-core"
+license = "MIT"
+
+[lib]
+crate-type = ["cdylib", "staticlib"]
+
+[dependencies]
+engram-core = { path = "../engram-core" }
+uuid = { version = "1", features = ["v4", "serde"] }
+
+[dev-dependencies]
+tempfile = "3"