fix: improve database schema handling and add migration feature gate

- Fix column name quoting in ALTER TABLE statements to prevent SQL
  syntax errors with reserved keywords
- Use case-insensitive table name matching in table_exists()
- Change type declarations from INTEGER to BOOLEAN for semantic clarity
- Add CC_SWITCH_ENABLE_JSON_DB_MIGRATION env var to gate JSON→SQLite
  migration (disabled by default until feature is stable)
- Refactor tests with shared legacy schema and column info helpers
- Add comprehensive test for column types and default values alignment

src-tauri/src/lib.rs

@@ -113,6 +113,17 @@ const TRAY_SECTIONS: [TrayAppSection; 3] = [
     },
 ];
 
+/// 读取类似布尔的环境变量（1/true/yes/on 视为开启）
+fn env_flag_enabled(key: &str) -> bool {
+    match std::env::var(key) {
+        Ok(val) => matches!(
+            val.trim().to_ascii_lowercase().as_str(),
+            "1" | "true" | "yes" | "on"
+        ),
+        Err(_) => false,
+    }
+}
+
 fn append_provider_section<'a>(
     app: &'a tauri::AppHandle,
     mut menu_builder: MenuBuilder<'a, tauri::Wry, tauri::AppHandle<tauri::Wry>>,
@@ -542,8 +553,9 @@ pub fn run() {
             let db_path = app_config_dir.join("cc-switch.db");
             let json_path = app_config_dir.join("config.json");
 
-            // Check if migration is needed (DB doesn't exist but JSON does)
-            let migration_needed = !db_path.exists() && json_path.exists();
+            // 检查是否需要从 config.json 迁移到 SQLite，功能尚未正式发布，默认关闭
+            let migration_opt_in = env_flag_enabled("CC_SWITCH_ENABLE_JSON_DB_MIGRATION");
+            let migration_needed = !db_path.exists() && json_path.exists() && migration_opt_in;
 
             let db = match crate::database::Database::init() {
                 Ok(db) => Arc::new(db),
@@ -555,8 +567,12 @@ pub fn run() {
                 }
             };
 
-            if migration_needed {
-                log::info!("Starting migration from config.json to SQLite...");
+            if !migration_opt_in && !db_path.exists() && json_path.exists() {
+                log::warn!(
+                    "检测到 config.json，但 JSON→数据库迁移功能尚未正式发布，默认跳过。设置 CC_SWITCH_ENABLE_JSON_DB_MIGRATION=1 后再尝试。"
+                );
+            } else if migration_needed {
+                log::info!("Starting migration from config.json to SQLite (opt-in)...");
                 match crate::app_config::MultiAppConfig::load() {
                     Ok(config) => {
                         if let Err(e) = db.migrate_from_json(&config) {