feat: 矢量占位美术素材（海面/敌机/子弹/道具/Boss/地面单位）

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

assets/svg/ship.svg

@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 48 136">
+  <!-- 驱逐舰（俯视，舰艏朝上） -->
+  <ellipse cx="24" cy="126" rx="12" ry="7" fill="#dff0f8" opacity="0.45"/>
+  <polygon points="24,2 34,26 36,96 30,118 18,118 12,96 14,26" fill="#6e7d8a"/>
+  <polygon points="24,2 34,26 35,60 13,60 14,26" fill="#7d8c99"/>
+  <rect x="22" y="30" width="4" height="82" fill="#5d6b77"/>
+  <!-- 前后炮塔 -->
+  <rect x="18" y="34" width="12" height="12" rx="3" fill="#4d5a64"/>
+  <rect x="18" y="92" width="12" height="12" rx="3" fill="#4d5a64"/>
+  <rect x="22" y="26" width="4" height="9" fill="#3a454d"/>
+  <rect x="22" y="104" width="4" height="9" fill="#3a454d"/>
+  <!-- 舰桥与烟囱 -->
+  <rect x="16" y="56" width="16" height="18" rx="3" fill="#5d6b77"/>
+  <rect x="19" y="59" width="10" height="8" rx="2" fill="#8fa8b8"/>
+  <rect x="20" y="78" width="8" height="10" rx="2" fill="#3f4a52"/>
+  <!-- 舰艏波与舰艉水沫 -->
+  <path d="M10 20 q14 -10 28 0" stroke="#dff0f8" stroke-width="2.4" fill="none" opacity="0.55"/>
+  <ellipse cx="24" cy="122" rx="6" ry="10" fill="#eef7fb" opacity="0.35"/>
+</svg>