Migrate to CMake-based build with packaging

Major build system refactoring:

**CMake (build authority)**:
- Auto-discovers .cpp files (GLOB_RECURSE in source/core/ and source/game/)
- No manual file list maintenance needed
- Excludes source/legacy/ automatically
- Generates build/project.h from template

**Makefile (simplified wrapper)**:
- Delegates compilation to CMake (make → cmake --build build)
- Contains 5 release packaging targets:
  * macos_release: .app bundle + .dmg (Apple Silicon)
  * linux_release: .tar.gz
  * windows_release: .zip with .exe + DLLs
  * windows_cross: cross-compile from Linux/macOS
  * rpi_release: ARM64 cross-compile
- Complex packaging logic preserved (code signing, symlinks, DMG creation)

**Benefits**:
- Add new .cpp file → automatically compiled (no manual updates)
- Single source of truth in CMakeLists.txt (no duplication)
- IDE-friendly (VSCode, CLion, etc.)
- Complete packaging support (5 platforms)

**Files changed**:
- CMakeLists.txt: GLOB_RECURSE replaces 23-file hardcoded list
- Makefile: Simplified compilation + added 5 release targets (~220 lines)
- CLAUDE.md: Updated build system documentation
- escena_titol.cpp: Fixed include path (build/project.h → project.h)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -12,59 +12,98 @@ This is **Orni Attack**, an **Asteroids-style game** originally written in **Tur
 
 ## Build System
 
-Based on `/home/sergio/gitea/pollo` project structure.
+Based on `/home/sergio/gitea/pollo` project structure, now with **CMake as build authority** and **automatic file discovery**.
 
-### Build Commands
+### Basic Build Commands
 
 ```bash
-# Clean + compile
-make clean && make
+make           # Compile (delegates to CMake)
+make debug     # Debug build
+make clean     # Clean artifacts
+./orni         # Run
+```
 
-# Run
-./orni
+### Release Packaging
 
-# Individual targets
-make linux    # Linux build
-make macos    # macOS build
-make windows  # Windows build (MinGW)
+```bash
+make macos_release     # macOS .app bundle + .dmg (Apple Silicon)
+make linux_release     # Linux .tar.gz
+make windows_release   # Windows .zip (requires MinGW on Windows)
+make windows_cross     # Cross-compile Windows from Linux/macOS
+make rpi_release       # Raspberry Pi ARM64 cross-compile
 ```
 
 ### Build Files
 
-- **CMakeLists.txt** - CMake configuration (C++20, SDL3, project metadata)
-- **Makefile** - Cross-platform wrapper, extracts project info from CMakeLists.txt
+- **CMakeLists.txt** - CMake configuration (C++20, SDL3, auto-discovers .cpp files)
+- **Makefile** - Wrapper for compilation + complex packaging recipes
 - **source/project.h.in** - Template for auto-generated project.h
 - **build/project.h** - Auto-generated (by CMake) with project constants
-- **release/** - Platform-specific resources (icons, .rc, .plist)
+- **release/** - Platform-specific resources (icons, .rc, .plist, frameworks, DLLs)
+
+### Architecture: Hybrid CMake + Makefile
+
+**CMake handles**: Compilation (simple, standard, IDE-friendly)
+- Auto-discovers all `.cpp` files in `source/core/` and `source/game/`
+- Excludes `source/legacy/` automatically
+- Generates `build/project.h` from template
+- Links SDL3
+
+**Makefile handles**: Packaging (complex bash scripts)
+- Delegates compilation to CMake (`make` → `cmake --build build`)
+- Contains 5 release packaging targets (macOS, Linux, Windows, RPI, Windows-cross)
+- Includes: code signing, framework symlinks, DMG creation, cross-compilation
 
 ### Project Metadata System
 
-**Auto-generation with CMake**:
+**Single source of truth** in `CMakeLists.txt`:
 
-CMake generates `build/project.h` from `source/project.h.in` template on every compilation:
+```cmake
+project(orni VERSION 0.3.0)
+set(PROJECT_LONG_NAME "Orni Attack")
+set(PROJECT_COPYRIGHT "© 1999 Visente i Sergi, 2025 Port")
+```
+
+**Auto-generated** `build/project.h`:
 
 ```cpp
-// build/project.h (generated automatically)
 namespace Project {
-    constexpr const char* NAME = "orni";              // From project(orni ...)
-    constexpr const char* LONG_NAME = "Orni Attack";  // From PROJECT_LONG_NAME
-    constexpr const char* VERSION = "0.1.0";          // From VERSION
-    constexpr const char* COPYRIGHT = "© 1999...";    // From PROJECT_COPYRIGHT
-    constexpr const char* GIT_HASH = "abc1234";       // From git rev-parse
+    constexpr const char* NAME = "orni";
+    constexpr const char* LONG_NAME = "Orni Attack";
+    constexpr const char* VERSION = "0.3.0";
+    constexpr const char* COPYRIGHT = "© 1999 Visente i Sergi, 2025 Port";
+    constexpr const char* GIT_HASH = "abc1234";  // From git rev-parse
 }
 ```
 
-**Window title format** (dynamic, in sdl_manager.cpp):
-```cpp
-std::format("{} v{} ({})",
-    Project::LONG_NAME,    // "Orni Attack"
-    Project::VERSION,      // "0.1.0"
-    Project::COPYRIGHT)    // "© 1999 Visente i Sergi, 2025 Port"
+**Window title** (dynamic): `Orni Attack v0.3.0 (© 1999 Visente i Sergi, 2025 Port)`
+
+### File Discovery
+
+**Automatic** - no manual maintenance needed:
+
+```cmake
+# CMakeLists.txt automatically finds:
+file(GLOB_RECURSE CORE_SOURCES "source/core/*.cpp")
+file(GLOB_RECURSE GAME_SOURCES "source/game/*.cpp")
+# + source/main.cpp
+# - source/legacy/* (excluded)
 ```
 
-Result: `Orni Attack v0.1.0 (© 1999 Visente i Sergi, 2025 Port)`
+**When you create a new file** like `source/game/entities/asteroide.cpp`:
+1. Just create it in the appropriate directory
+2. Run `make`
+3. CMake automatically detects and compiles it
 
-**Single source of truth**: All project info in CMakeLists.txt, no hardcoded strings.
+**No need to edit** Makefile or CMakeLists.txt!
+
+### Cross-Platform Notes
+
+- **macOS**: Requires `create-dmg` (auto-installed via Homebrew)
+- **Windows**: Compile natively with MinGW or use `make windows_cross` on Linux/macOS
+- **Windows cross**: Requires `x86_64-w64-mingw32-g++` toolchain
+- **RPI cross**: Requires `aarch64-linux-gnu-g++` toolchain
+- **Frameworks**: macOS release includes SDL3.xcframework with symlink recreation
 
 ## Architecture