feat(rust): split core library into activate/license/heartbeat modules with build.rs and C ABI tests

native/craft-core/src/activate.rs

@@ -0,0 +1,9 @@
+// Activation logic — communicates with BitAnswer cloud or self-hosted backend
+
+use crate::CraftResult;
+
+/// Core activation logic — communicates with BitAnswer cloud or self-hosted backend
+pub fn core_activate(_license_key: &str, _config_json: &str) -> CraftResult {
+    // TODO: actual network communication based on config provider
+    crate::ok_result()
+}