refactor: use stateless identity fallback

modules/core/vehicle-identity/src/main/java/com/lingniu/ingest/identity/StatelessVehicleIdentityResolver.java

@@ -0,0 +1,34 @@
+package com.lingniu.ingest.identity;
+
+/**
+ * Stateless production fallback used when a caller has no injected identity service.
+ *
+ * <p>Persistent binding belongs to {@link MySqlVehicleIdentityService}; this resolver only keeps
+ * ingestion flowing with explicit VIN or stable external identifiers.
+ */
+public final class StatelessVehicleIdentityResolver implements VehicleIdentityResolver {
+
+    @Override
+    public VehicleIdentity resolve(VehicleIdentityLookup lookup) {
+        if (lookup == null) {
+            return unknown();
+        }
+        if (!lookup.vin().isBlank()) {
+            return new VehicleIdentity(lookup.vin(), true, VehicleIdentitySource.EXPLICIT_VIN);
+        }
+        if (!lookup.deviceId().isBlank()) {
+            return new VehicleIdentity(lookup.deviceId(), false, VehicleIdentitySource.FALLBACK_DEVICE_ID);
+        }
+        if (!lookup.phone().isBlank()) {
+            return new VehicleIdentity(lookup.phone(), false, VehicleIdentitySource.FALLBACK_PHONE);
+        }
+        if (!lookup.plate().isBlank()) {
+            return new VehicleIdentity(lookup.plate(), false, VehicleIdentitySource.FALLBACK_PLATE);
+        }
+        return unknown();
+    }
+
+    private static VehicleIdentity unknown() {
+        return new VehicleIdentity("unknown", false, VehicleIdentitySource.UNKNOWN);
+    }
+}