feat: 问题数据迁移到数据库；学员详情页URL导航改造；侧边栏统一

- 问题从文件系统迁移到数据库 problems 表
- 移除 PROBLEMS_DIR 配置和文件读取逻辑
- student.html 完整重写：编辑/添加/删除问题，生成方案进度显示
- 学员详情页支持独立URL访问 (/student/<id>)
- 统一侧边栏到 base.html
- 更新文档：DEPLOYMENT_SOP, MODELS, STRUCTURE, FRONTEND_ARCH
- 部署到生产环境 v1.2.0

app/routes/students.py

@@ -15,18 +15,46 @@ from app.routes import main_bp
 from app.models import (
     db,
     Student,
+    Class,
+    PracticePlan,
     PROBLEM_LIST,
     SEVERITY_LEVELS,
     PRACTICE_TIME_OPTIONS,
     User,
-    Class,
 )
 from app.routes.auth import login_required_json, check_login
 
 
 @main_bp.route("/")
 def index():
-    """首页 - 学员列表"""
+    """首页"""
+    if not check_login():
+        return redirect("/login")
+
+    student_count = Student.query.count()
+    class_count = Class.query.count()
+    plan_count = PracticePlan.query.count()
+
+    return render_template(
+        "home.html",
+        student_count=student_count,
+        class_count=class_count,
+        plan_count=plan_count,
+        active_nav="home",
+    )
+
+
+@main_bp.route("/student/<int:student_id>")
+@login_required_json
+def student_detail_page(student_id):
+    """学员详情页"""
+    student = Student.query.get_or_404(student_id)
+    return render_template("student.html", student=student, active_nav="students")
+
+
+@main_bp.route("/students")
+def students_page():
+    """学员列表页"""
     if not check_login():
         return redirect("/login")
 
@@ -35,6 +63,7 @@ def index():
         problem_list=PROBLEM_LIST,
         severity_levels=SEVERITY_LEVELS,
         practice_time_options=PRACTICE_TIME_OPTIONS,
+        active_nav="students",
     )