feat(log): introdueix Log:: wrapper sobre SDL_Log

Logger lleuger a source/utils/log.{hpp,cpp} amb API basada en std::format
i filtre runtime via la variable d'entorn AEE_LOG (sintaxi
*:info,Resource::Helper:warn,scene:debug). Substitueix gradualment els
std::cout/cerr dispersos.

- Categories CUSTOM registrades sota demanda; per defecte INFO.
- Categories SDL natives no es toquen tret que l'usuari posi *:level.
- Migra resource_helper.cpp i els marcadors d'inici/fi (main.cpp) com a
  testimoni; la resta de subsistemes es migra en commits següents.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

source/core/resources/resource_helper.cpp

@@ -1,12 +1,12 @@
 #include "core/resources/resource_helper.hpp"
 
 #include <fstream>
-#include <iostream>
 #include <string>
 #include <string_view>
 
 #include "core/resources/resource_pack.hpp"
 #include "utils/defaults.hpp"
+#include "utils/log.hpp"
 
 namespace Resource::Helper {
 
@@ -27,14 +27,14 @@ namespace Resource::Helper {
                 // Silenciem si veníem de prefer_disk: aleshores caurem
                 // al pack i no és cap error real que el fitxer no estigui
                 // al disc.
-                if (verbose) { std::cerr << "Resource::Helper: cannot open " << FULL << '\n'; }
+                if (verbose) { Log::error("Resource::Helper", "cannot open {}", FULL); }
                 return {};
             }
             std::streamsize size = file.tellg();
             file.seekg(0, std::ios::beg);
             std::vector<std::uint8_t> data(static_cast<std::size_t>(size));
             if (!file.read(reinterpret_cast<char*>(data.data()), size)) {
-                std::cerr << "Resource::Helper: failed to read " << FULL << '\n';
+                Log::error("Resource::Helper", "failed to read {}", FULL);
                 return {};
             }
             return data;
@@ -52,14 +52,11 @@ namespace Resource::Helper {
         g_pack_loaded = g_pack.loadPack(pack_file);
 
         if (g_pack_loaded) {
-            std::cout << "Resource::Helper: pack loaded (" << g_pack.getResourceCount()
-                      << " entries) from " << pack_file << '\n';
+            Log::info("Resource::Helper", "pack loaded ({} entries) from {}", g_pack.getResourceCount(), pack_file);
         } else if (enable_fallback) {
-            std::cout << "Resource::Helper: no pack at " << pack_file
-                      << " — using filesystem fallback\n";
+            Log::info("Resource::Helper", "no pack at {} — using filesystem fallback", pack_file);
         } else {
-            std::cerr << "Resource::Helper: FATAL — no pack at " << pack_file
-                      << " and fallback disabled\n";
+            Log::critical("Resource::Helper", "FATAL — no pack at {} and fallback disabled", pack_file);
             return false;
         }
         return true;