refactor(core): replace JSON-based pipeline with MySQL database

This commit introduces a major architectural overhaul, migrating the data backend from a flat JSON
file to a relational MySQL database.

- Replaced multiple scraping scripts with a unified `main.py` that handles crawling, parsing, and
database synchronization.
- Introduced `mysql_helper.py` for robust database interaction with a connection pool.
- Added `queries.sql` defining the new database schema for assets, categories, tags, and changelogs.
- Removed all obsolete frontend code (v1, v2) and old scraping scripts.

This change provides a more scalable and maintainable foundation for managing asset data.

mysql_helper.py

@@ -0,0 +1,145 @@
+from mysql.connector import pooling, Error
+import logging
+from contextlib import contextmanager
+import time
+
+# ========== 日志配置 ==========
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s [%(levelname)s] %(message)s"
+)
+logger = logging.getLogger("MySQLHelper")
+
+class MySQLHelper:
+    def __init__(self, host, user, password, database, pool_size=5):
+        """
+        初始化 MySQL 连接池
+        """
+        try:
+            self.pool = pooling.MySQLConnectionPool(
+                pool_name="mypool",
+                pool_size=pool_size,
+                pool_reset_session=True,
+                host=host,
+                user=user,
+                password=password,
+                database=database,
+                charset="utf8mb4"
+            )
+            logger.info("✅ MySQL 连接池已创建，大小=%s", pool_size)
+        except Error as e:
+            logger.error("❌ 创建连接池失败: %s", e)
+            raise
+
+    @contextmanager
+    def get_conn(self):
+        """
+        获取连接并在使用完毕后释放
+        """
+        conn = None
+        try:
+            conn = self.pool.get_connection()
+            yield conn
+        except Error as e:
+            logger.error("数据库连接错误: %s", e)
+            raise
+        finally:
+            if conn:
+                conn.close()
+
+    def execute(self, sql, params=None, commit=False, retry=3):
+        """
+        执行 INSERT/UPDATE/DELETE 等操作
+        """
+        for attempt in range(1, retry + 1):
+            try:
+                with self.get_conn() as conn:
+                    cursor = conn.cursor()
+                    cursor.execute(sql, params or ())
+                    if commit:
+                        conn.commit()
+                    affected = cursor.rowcount
+                    cursor.close()
+                    return affected
+            except Error as e:
+                logger.warning("执行 SQL 失败 (尝试 %s/%s): %s", attempt, retry, e)
+                time.sleep(1)
+                if attempt == retry:
+                    raise
+
+    def fetch_all(self, sql, params=None, retry=3):
+        """
+        查询多条记录
+        """
+        for attempt in range(1, retry + 1):
+            try:
+                with self.get_conn() as conn:
+                    cursor = conn.cursor(dictionary=True)
+                    cursor.execute(sql, params or ())
+                    result = cursor.fetchall()
+                    cursor.close()
+                    return result
+            except Error as e:
+                logger.warning("查询失败 (尝试 %s/%s): %s", attempt, retry, e)
+                time.sleep(1)
+                if attempt == retry:
+                    raise
+
+    def fetch_one(self, sql, params=None, retry=3):
+        """
+        查询单条记录
+        """
+        result = self.fetch_all(sql, params, retry)
+        return result[0] if result else None
+    
+    def bulk_insert(self, sql: str, rows: list[tuple]):
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.executemany(sql, rows)
+            conn.commit()
+            cursor.close()
+
+    @contextmanager
+    def transaction(self):
+        """
+        事务上下文管理器
+        用法:
+        with db.transaction() as cursor:
+            cursor.execute(...)
+            cursor.execute(...)
+        """
+        with self.get_conn() as conn:
+            try:
+                cursor = conn.cursor()
+                yield cursor
+                conn.commit()
+            except:
+                conn.rollback()
+                raise
+            finally:
+                cursor.close()
+
+# ================= 使用示例 =================
+if __name__ == "__main__":
+    db = MySQLHelper(
+        host="localhost",
+        user="root",
+        password="123456",
+        database="test_db",
+        pool_size=5
+    )
+
+    # 插入数据
+    db.execute("INSERT INTO users(name, age) VALUES (%s, %s)", ("Alice", 25), commit=True)
+
+    # 查询数据
+    users = db.fetch_all("SELECT * FROM users WHERE age > %s", (18,))
+    logger.info("查询结果: %s", users)
+
+    # 事务示例
+    try:
+        with db.transaction() as cur:
+            cur.execute("UPDATE users SET age = age + 1 WHERE name = %s", ("Alice",))
+            cur.execute("INSERT INTO logs(message) VALUES (%s)", ("Alice age updated",))
+    except Error as e:
+        logger.error("事务失败: %s", e)