feat: add profile avatar selection and enhance sidebar UI with icons

backend/src/models/user/user.rs

@@ -41,6 +41,9 @@ pub struct Model {
     /// Foreign key to diet types
     pub diet_id: Option<i32>,
 
+    /// URL to profile avatar icon
+    pub avatar_url: Option<String>,
+
     pub created_at: DateTime,
     pub updated_at: DateTime,
 }