feat: 侧边栏分组图标与导航样式优化

- 分组支持 icon 字段，可按名称自动匹配或手动选择
- 左侧导航与总览卡片显示彩色 SVG 图标
- 优化侧栏链接圆角与选中态样式

Co-authored-by: Cursor <cursoragent@cursor.com>

models.py

@@ -24,6 +24,7 @@ class ServiceGroup(db.Model):
 
     id = db.Column(db.Integer, primary_key=True)
     name = db.Column(db.String(120), nullable=False)
+    icon = db.Column(db.String(16), nullable=False, default="", server_default="")
     sort_order = db.Column(db.Integer, nullable=False, default=0)
 
     services = db.relationship(
@@ -33,6 +34,26 @@ class ServiceGroup(db.Model):
         cascade="all, delete-orphan",
     )
 
+    def resolve_icon_key(self) -> str:
+        key = (self.icon or "").strip().lower()
+        if key:
+            return key
+        name = self.name or ""
+        lower = name.lower()
+        if "下单" in name:
+            return "order"
+        if "交易" in name:
+            return "trade"
+        if "复盘" in name:
+            return "review"
+        if "api" in lower:
+            return "api"
+        if "gate" in lower or "扫单" in name:
+            return "gate"
+        if "k线" in lower or "k 线" in name or "chart" in lower:
+            return "chart"
+        return "folder"
+
 
 class Service(db.Model):
     __tablename__ = "services"