ci(sec): improve type safety and server organization in HTTP middleware (#4437)

- Update linting configuration to exclude G115 gosec check instead of including specific checks
- Add the safeInt8 helper for safer type conversions and use it to prevent int8 overflow in middleware handler execution
- Group related constants and variables together for better organization in gin.go
- Refactor HTTP server instantiation to use a dedicated http.Server object for all Run methods
- Add the safeUint16 helper and use it to safely handle conversions in tree node functions to prevent uint16 overflow

Signed-off-by: appleboy <appleboy.tw@gmail.com>