feat: fully implement profile controller;

feat: implement file upload handling in controller with size and type validation;
feat: add custom validation rules for bio and color hex fields;
refactor: enhance request handling with dedicated client info extraction;
chore: update profile DTOs with validation tags;
docs: profile controller swagger

backend/internal/errors/general.go

@@ -26,4 +26,5 @@ var (
 	ErrBadRequest = errors.New("Bad request")
 	ErrForbidden = errors.New("Access is denied")
 	ErrTooManyRequests = errors.New("Too many requests")
+	ErrNotFound = errors.New("Resource not found")
 )