Add brand-specific update channel and environment configuration

- Updated `brand_config.py` to include `WEBDROP_UPDATE_CHANNEL` in the environment variables.
- Enhanced `build_macos.sh` to create a bundled `.env` file with brand-specific defaults, including the update channel.
- Implemented a method in `build_windows.py` to create a bundled `.env` file for Windows builds, incorporating brand-specific runtime defaults.
- Modified `config.py` to ensure the application can locate the `.env` file in various installation scenarios.
- Added unit tests in `test_config.py` to verify the loading of the bootstrap `.env` from the PyInstaller runtime directory.
- Generated new WiX object and script files for the Windows installer, including application shortcuts and registry entries.

tests/unit/test_config.py

@@ -1,6 +1,7 @@
 """Unit tests for configuration system."""
 
 import os
+import sys
 
 import pytest
 
@@ -232,3 +233,22 @@ class TestConfigValidation:
 
         assert config_path.parts[-2:] == ("agravity_bridge", "config.json")
         assert log_path.parts[-2:] == ("logs", "agravity_bridge.log")
+
+
+class TestBootstrapEnvLoading:
+    """Test bootstrap .env loading behavior for packaged builds."""
+
+    def test_load_bootstrap_env_reads_meipass_dotenv(self, tmp_path, monkeypatch):
+        """Packaged app should load .env from PyInstaller runtime directory."""
+        meipass_dir = tmp_path / "runtime"
+        meipass_dir.mkdir(parents=True)
+        env_path = meipass_dir / ".env"
+        env_path.write_text("APP_NAME=Agravity Bridge\n", encoding="utf-8")
+
+        monkeypatch.setattr(sys, "frozen", True, raising=False)
+        monkeypatch.setattr(sys, "_MEIPASS", str(meipass_dir), raising=False)
+
+        loaded_path = Config.load_bootstrap_env()
+
+        assert loaded_path == env_path
+        assert os.getenv("APP_NAME") == "Agravity Bridge"