feat(linter): afegir checks llvm-include-order i misc-include-cleaner

- Check 11: llvm-include-order (0 errors - codi ja compleix)
- Check 12: misc-include-cleaner (detectar includes no usats i faltants)
  - Configurar IgnoreHeaders per SDL3 (genera falsos positius)
  - Fix: afegir <cstdint> a nau.hpp, enemic.hpp, bala.hpp
  - Fix: afegir <cmath> a nau.hpp, enemic.hpp (std::cos/sin)

Include order validat segons LLVM coding standards.
Headers més nets i compilació més ràpida.

.clang-tidy

@@ -31,6 +31,10 @@ Checks:
   - -bugprone-switch-missing-default-case       # Excluido (no todos los switches necesitan default)
   - -bugprone-implicit-widening-of-multiplication-result  # Excluido (valores pequeños, sin overflow)
   - -bugprone-exception-escape                  # Excluido (excepciones en main terminan el programa - OK)
+  # ✅ Check 11: llvm-include-order (validar orden de includes - 0 errores)
+  - llvm-include-order
+  # ⏳ Check 12: misc-include-cleaner (detectar includes no usados y faltantes)
+  - misc-include-cleaner
 
 WarningsAsErrors: '*'
 # No usar HeaderFilterRegex - usamos .clang-tidy local en source/core/audio/ para excluir
@@ -95,3 +99,6 @@ CheckOptions:
 
   # Parámetros en lower_case
   - { key: readability-identifier-naming.ParameterCase, value: lower_case }
+
+  # misc-include-cleaner: Ignorar SDL (genera falsos positivos)
+  - { key: misc-include-cleaner.IgnoreHeaders, value: 'SDL3/.*' }