更新方形Logo和头颈部CT默认分类

- 侧边栏 Logo 改为导入根目录 logo_square.png，favicon 也切换为 /logo_square.png，并让前端服务显式提供该根目录图片。

- 头颈部CT分割默认模板分类名改为纯中文，去掉括号英文翻译，颜色和 maskid 保持用户给定顺序。

- 增加旧版头颈部CT英文括号 label 的窄迁移，启动 seed 时自动把旧默认系统模板更新为纯中文默认。

- 更新前端 Logo 测试、后端默认模板和恢复出厂设置测试，覆盖纯中文分类和根目录方形 Logo。

- 更新 AGENTS、README、前端审计、需求冻结和测试计划文档，记录根目录 Logo 和头颈部CT纯中文默认分类。

backend/tests/test_templates.py

@@ -55,16 +55,16 @@ def test_default_head_neck_ct_template_is_seeded_and_visible(client, db_session)
     head_neck = next(template for template in listing.json() if template["name"] == "头颈部CT分割")
     assert head_neck["description"] == "头颈部CT分割"
     expected_names = [
-        "肿瘤/结节 (Tumor/Nodule)",
-        "下颌骨 (Mandible)",
-        "甲状腺 (Thyroid)",
-        "气管 (Trachea)",
-        "颈椎 (Cervical Spine)",
-        "颈动脉 (Carotid Artery)",
-        "颈静脉 (Jugular Vein)",
-        "腮腺 (Parotid Gland)",
-        "下颌下腺 (Submandibular Gland)",
-        "舌骨 (Hyoid Bone)",
+        "肿瘤/结节",
+        "下颌骨",
+        "甲状腺",
+        "气管",
+        "颈椎",
+        "颈动脉",
+        "颈静脉",
+        "腮腺",
+        "下颌下腺",
+        "舌骨",
         "待分类",
     ]
     expected_colors = [
@@ -89,3 +89,32 @@ def test_default_head_neck_ct_template_is_seeded_and_visible(client, db_session)
         raise AssertionError(f"Unexpected head-neck colors: {actual_colors}")
     if actual_mask_ids != [*list(range(1, 11)), 0]:
         raise AssertionError(f"Unexpected head-neck mask IDs: {actual_mask_ids}")
+
+
+def test_default_head_neck_ct_template_migrates_legacy_english_labels(db_session):
+    from main import ensure_default_templates
+    from models import Template
+
+    db_session.add(Template(
+        name="头颈部CT分割",
+        description="legacy",
+        color="#ef4444",
+        z_index=10,
+        owner_user_id=None,
+        mapping_rules={
+            "classes": [
+                {"id": "old-1", "name": "肿瘤/结节 (Tumor/Nodule)", "color": "#ff0000", "zIndex": 10, "maskId": 1},
+                {"id": "reserved-unclassified", "name": "待分类", "color": "#000000", "zIndex": 0, "maskId": 0},
+            ],
+            "rules": [],
+        },
+    ))
+    db_session.commit()
+
+    ensure_default_templates(db_session)
+
+    templates = db_session.query(Template).filter(Template.name == "头颈部CT分割").all()
+    assert len(templates) == 1
+    classes = templates[0].mapping_rules["classes"]
+    assert classes[0]["name"] == "肿瘤/结节"
+    assert all("(" not in item["name"] for item in classes)