feat(rust): add Provider trait + refactor C ABI to route through Provider

SelfHostedProvider implements Provider trait for offline license verification

native/craft-core/src/trait_provider.rs

@@ -0,0 +1,36 @@
+use std::collections::HashMap;
+use crate::{CraftContext, LicenseInfo, error::LicenseError};
+
+#[derive(Debug)]
+pub struct LicenseStatus {
+    pub licensed: bool,
+    pub not_after: Option<i64>,
+    pub features: HashMap<String, bool>,
+    pub device_count: u32,
+    pub max_devices: u32,
+    pub heartbeat_due: Option<i64>,
+}
+
+pub struct ActivateResponse {
+    pub success: bool,
+    pub device_id: String,
+    pub license_payload: Vec<u8>,
+}
+
+pub struct HeartbeatResponse {
+    pub valid: bool,
+    pub lease_until: Option<i64>,
+    pub update_available: bool,
+    pub new_license_payload: Option<Vec<u8>>,
+}
+
+pub trait Provider: Send + Sync {
+    fn initialize(&mut self, ctx: &CraftContext, config_json: &str) -> Result<(), LicenseError>;
+    fn activate(&self, ctx: &CraftContext, license_key: &str) -> Result<ActivateResponse, LicenseError>;
+    fn check_license(&self, ctx: &CraftContext) -> Result<LicenseStatus, LicenseError>;
+    fn heartbeat(&self, ctx: &CraftContext) -> Result<HeartbeatResponse, LicenseError>;
+    fn has_feature(&self, ctx: &CraftContext, name: &str) -> bool;
+    fn release(&mut self) -> Result<(), LicenseError>;
+    fn get_license_info(&self, ctx: &CraftContext) -> LicenseInfo;
+    fn close(&mut self);
+}