doc: update backend doc

assets/coconut-leaf.template.toml

@@ -1,10 +1,12 @@
+# Driver: "sqlite" or "mysql"
 [database]
 driver = "sqlite"
 
+# Path to the SQLite database file
 [database.config]
 path = "coconut-leaf.db"
 
-# MySQL（占位，尚未实现）
+# MySQL connection parameters (placeholder, not yet implemented)
 # [database]
 # driver = "mysql"
 #
@@ -15,9 +17,12 @@ path = "coconut-leaf.db"
 # password = "password"
 # database = "coconut_leaf"
 
+# HTTP listening port
 [web]
 port = 8848
 
 [others]
-auto-token-clean-duration = 86400   # 自动清理过期 token 的间隔（秒）
-debug = true                        # 开启后日志级别降到 DEBUG
+# Interval (in seconds) for automatic cleanup of expired tokens
+auto-token-clean-duration = 86400
+# Debug mode; must be set to false in production
+debug = true