fix: instantiate MovementComponent as this.movement in Unit base class

Infantry/Tank call this.movement.shouldUpdate() but Unit stored movement
config as a plain object in this.components. Import MovementComponent and
expose it as this.movement so subclasses get the real instance with shouldUpdate().

src/entities/Unit.js

@@ -1,5 +1,6 @@
 import Phaser from 'phaser';
 import EntityStateMachine from 'Systems/EntityStateMachine';
+import MovementComponent from 'Entities/components/MovementComponent';
 
 /**
  * Unit Entity - Component-based architecture
@@ -60,6 +61,9 @@ export default class Unit extends Phaser.Physics.Arcade.Sprite {
     this.dead = false;
     this.setInteractive({ pixelPerfect: true });
 
+    // Expose MovementComponent as this.movement (expected by subclasses)
+    this.movement = new MovementComponent(this, config.movement || {});
+
     // Initialize state machine
     this.stateMachine = null;
     this._initStateMachine();