fix: 标签保存+管理功能

- 修复 create_diary 不保存 tags 的问题
- 新建标签后加入全局标签列表，移除后显示在候选区
- 标签筛选区：编辑者可新增标签，管理员可删除标签
- 标签筛选区每个标签旁加×删除按钮（管理员）

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/main.py

@@ -1238,14 +1238,15 @@ def create_diary(body: dict, user=Depends(get_current_user)):
     name = body.get("name", "").strip()
     ingredients = body.get("ingredients", [])
     note = body.get("note", "")
+    tags = body.get("tags", [])
     source_id = body.get("source_recipe_id")
     if not name:
         raise HTTPException(400, "请输入配方名称")
     conn = get_db()
     c = conn.cursor()
     c.execute(
-        "INSERT INTO user_diary (user_id, source_recipe_id, name, ingredients, note) VALUES (?, ?, ?, ?, ?)",
-        (user["id"], source_id, name, json.dumps(ingredients, ensure_ascii=False), note)
+        "INSERT INTO user_diary (user_id, source_recipe_id, name, ingredients, note, tags) VALUES (?, ?, ?, ?, ?, ?)",
+        (user["id"], source_id, name, json.dumps(ingredients, ensure_ascii=False), note, json.dumps(tags, ensure_ascii=False))
     )
     conn.commit()
     did = c.lastrowid