refactor: centralize configuration management with type-safe schema

Major changes:
- Add dataclass-based configuration schema with validation (config/schema.py)
- Create centralized config loader and default values (config/defaults.py, config/loader.py)
- Remove duplicate database_config.py, merge into unified structure
- Consolidate browser settings into ERP config
- Add batch_size parameter support to extractor

Bug fixes:
- Fix settings save error by updating config paths (browser.* → erp.*)
- Fix batch_size not being applied in data extraction

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

config/defaults.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+默认配置值
+
+定义所有配置项的默认值。
+"""
+from config.schema import (
+    ERPConfig,
+    DatabaseConfig,
+    PathConfig,
+    ExtractionConfig,
+    AppConfig
+)
+
+
+# 默认配置
+DEFAULT_APP_CONFIG = AppConfig(
+    erp=ERPConfig(
+        url="https://68.11.34.30:8082/",
+        username="BLDpengqiangqiang",
+        password="Cqbld123456.",
+        headless=True,
+        ignore_https_errors=True,
+        auto_close_browser=True,
+    ),
+    database=DatabaseConfig(
+        server="192.168.110.114",
+        database="CompanyDB",
+        username="peng",
+        password="Cqbld123456.",
+        driver="ODBC Driver 18 for SQL Server",
+        trust_server_certificate="yes",
+    ),
+    paths=PathConfig(
+        data_dir="D:/python/playwrite/data/",
+        production_id_file="ProductionID.txt",
+        default_output="离散备料计划维护_合并.xlsx",
+        validation_output="物料状态校验结果.xlsx",
+    ),
+    extraction=ExtractionConfig(
+        batch_size=100,
+        verbose=True,
+        auto_convert=True,
+        merge_batches=True,
+    )
+)
+
+
+# 兼容旧版本的字典格式
+DEFAULT_SETTINGS_DICT = DEFAULT_APP_CONFIG.to_dict()