新增语言学习后台服务

- 分类管理：支持分类的增删改查
- 单词管理：支持单词的增删改查，包含音标、释义、例句等字段
- 更新 README 项目说明

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/internal/repository/queries/category.sql.go

@@ -0,0 +1,122 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: category.sql
+
+package queries
+
+import (
+	"context"
+)
+
+const createCategory = `-- name: CreateCategory :one
+INSERT INTO categories (name, sort_order)
+VALUES ($1, $2)
+RETURNING id, name, sort_order, created_at, updated_at
+`
+
+type CreateCategoryParams struct {
+	Name      string `json:"name"`
+	SortOrder int32  `json:"sort_order"`
+}
+
+func (q *Queries) CreateCategory(ctx context.Context, arg CreateCategoryParams) (Category, error) {
+	row := q.db.QueryRow(ctx, createCategory, arg.Name, arg.SortOrder)
+	var i Category
+	err := row.Scan(
+		&i.ID,
+		&i.Name,
+		&i.SortOrder,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+	)
+	return i, err
+}
+
+const deleteCategory = `-- name: DeleteCategory :exec
+DELETE FROM categories WHERE id = $1
+`
+
+func (q *Queries) DeleteCategory(ctx context.Context, id int32) error {
+	_, err := q.db.Exec(ctx, deleteCategory, id)
+	return err
+}
+
+const getCategory = `-- name: GetCategory :one
+SELECT id, name, sort_order, created_at, updated_at
+FROM categories
+WHERE id = $1
+`
+
+func (q *Queries) GetCategory(ctx context.Context, id int32) (Category, error) {
+	row := q.db.QueryRow(ctx, getCategory, id)
+	var i Category
+	err := row.Scan(
+		&i.ID,
+		&i.Name,
+		&i.SortOrder,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+	)
+	return i, err
+}
+
+const listCategories = `-- name: ListCategories :many
+SELECT id, name, sort_order, created_at, updated_at
+FROM categories
+ORDER BY sort_order ASC, id ASC
+`
+
+func (q *Queries) ListCategories(ctx context.Context) ([]Category, error) {
+	rows, err := q.db.Query(ctx, listCategories)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	items := []Category{}
+	for rows.Next() {
+		var i Category
+		if err := rows.Scan(
+			&i.ID,
+			&i.Name,
+			&i.SortOrder,
+			&i.CreatedAt,
+			&i.UpdatedAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const updateCategory = `-- name: UpdateCategory :one
+UPDATE categories
+SET name = $2,
+    sort_order = $3,
+    updated_at = NOW()
+WHERE id = $1
+RETURNING id, name, sort_order, created_at, updated_at
+`
+
+type UpdateCategoryParams struct {
+	ID        int32  `json:"id"`
+	Name      string `json:"name"`
+	SortOrder int32  `json:"sort_order"`
+}
+
+func (q *Queries) UpdateCategory(ctx context.Context, arg UpdateCategoryParams) (Category, error) {
+	row := q.db.QueryRow(ctx, updateCategory, arg.ID, arg.Name, arg.SortOrder)
+	var i Category
+	err := row.Scan(
+		&i.ID,
+		&i.Name,
+		&i.SortOrder,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+	)
+	return i, err
+}