feat: add Turso (libSQL) storage support for EdgeOne deployment

- Add TursoAdapter implementing DatabaseAdapter interface using @libsql/client
- Add 'turso' storage type to db.ts storage selector (reuses D1Storage)
- Add init-turso.js script for database migration and admin initialization
- Add @libsql/client dependency to package.json
- Update next.config.js to exclude @libsql/client from client-side bundle
- Update edgeone-deploy.yml workflow with TURSO_URL and TURSO_TOKEN secrets
- Update edgeone-build.mjs runtime env keys to include Turso variables
- Update .env.edgeone.example with Turso deployment instructions
- Update README.md with Turso as recommended storage for EdgeOne

Turso provides free SQLite-compatible cloud database (libSQL) with:
- 500 databases, 9GB storage, 1B row reads/month on free tier
- HTTP API compatible with edge/serverless environments
- Full SQLite syntax compatibility, reuses existing migrations

src/lib/turso-adapter.ts

@@ -0,0 +1,159 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+/**
+ * Turso (libSQL) 适配器
+ *
+ * 将 @libsql/client API 转换为与 D1 兼容的接口
+ * Turso 基于 libSQL（SQLite 开源分支），SQL 语法与 D1/SQLite 完全兼容
+ *
+ * 适用于 EdgeOne Pages 等无内置数据库的边缘平台
+ *
+ * 注意：此模块仅在服务端使用，通过 webpack 配置排除客户端打包
+ */
+
+import { createClient, type Client } from '@libsql/client';
+import { DatabaseAdapter, D1PreparedStatement, D1Result } from './d1-adapter';
+
+/**
+ * Turso 适配器
+ *
+ * 使用 @libsql/client 包装为 D1 兼容接口
+ */
+export class TursoAdapter implements DatabaseAdapter {
+  private client: Client;
+
+  constructor(url: string, authToken: string) {
+    this.client = createClient({
+      url,
+      authToken,
+    });
+  }
+
+  prepare(query: string): D1PreparedStatement {
+    return new TursoPreparedStatement(this.client, query);
+  }
+
+  async batch(statements: D1PreparedStatement[]): Promise<D1Result[]> {
+    // Turso/libSQL 原生支持 batch
+    const libsqlStatements = statements.map(
+      (stmt) => (stmt as TursoPreparedStatement).toLibSQLBatch()
+    );
+    const results = await this.client.batch(libsqlStatements, 'write');
+    return results.map((result) => ({
+      success: true,
+      results: result.rows || [],
+      meta: {
+        changes: result.rowsAffected,
+        last_row_id:
+          result.lastInsertRowid !== undefined
+            ? Number(result.lastInsertRowid)
+            : null,
+      },
+    }));
+  }
+
+  async exec(query: string): Promise<void> {
+    await this.client.executeMultiple(query);
+  }
+}
+
+/**
+ * Turso PreparedStatement 包装器
+ * 将 @libsql/client API 转换为 D1 兼容 API
+ */
+class TursoPreparedStatement implements D1PreparedStatement {
+  private params: any[] = [];
+
+  constructor(
+    private client: Client,
+    private query: string
+  ) {}
+
+  bind(...values: any[]): D1PreparedStatement {
+    this.params = values;
+    return this;
+  }
+
+  /**
+   * 执行查询并返回第一行
+   */
+  async first<T = any>(colName?: string): Promise<T | null> {
+    try {
+      const result = await this.client.execute({
+        sql: this.query,
+        args: this.params,
+      });
+
+      if (!result.rows || result.rows.length === 0) return null;
+
+      const row = result.rows[0];
+      if (colName) return (row as any)[colName] ?? null;
+
+      return row as T;
+    } catch (err) {
+      console.error('Turso first() error:', err);
+      return null;
+    }
+  }
+
+  /**
+   * 执行查询并返回结果
+   */
+  async run<T = any>(): Promise<D1Result<T>> {
+    try {
+      const result = await this.client.execute({
+        sql: this.query,
+        args: this.params,
+      });
+
+      return {
+        success: true,
+        meta: {
+          changes: result.rowsAffected,
+          last_row_id:
+            result.lastInsertRowid !== undefined
+              ? Number(result.lastInsertRowid)
+              : null,
+        },
+        results: result.rows as T[],
+      };
+    } catch (err: any) {
+      console.error('Turso run() error:', err);
+      return {
+        success: false,
+        error: err.message,
+      };
+    }
+  }
+
+  /**
+   * 执行查询并返回所有行
+   */
+  async all<T = any>(): Promise<D1Result<T>> {
+    try {
+      const result = await this.client.execute({
+        sql: this.query,
+        args: this.params,
+      });
+
+      return {
+        success: true,
+        results: (result.rows || []) as T[],
+      };
+    } catch (err: any) {
+      console.error('Turso all() error:', err);
+      return {
+        success: false,
+        error: err.message,
+        results: [],
+      };
+    }
+  }
+
+  /**
+   * 转换为 libSQL batch 格式
+   */
+  toLibSQLBatch(): { sql: string; args: any[] } {
+    return { sql: this.query, args: this.params };
+  }
+}