feat: Add SHA256 checksum generation to Windows build script

- Automatically generate checksum file after building exe
- Checksum saved as WebDropBridge.exe.sha256
- Required for package uploads
- Also increase upload timeout to 600s for large files

build/scripts/build_windows.py

@@ -91,8 +91,30 @@ class WindowsBuilder:
         print(f"📦 Output: {exe_path}")
         print(f"   Size: {exe_path.stat().st_size / 1024 / 1024:.1f} MB")
 
+        # Generate SHA256 checksum
+        self.generate_checksum(exe_path)
+
         return True
 
+    def generate_checksum(self, file_path: Path) -> None:
+        """Generate SHA256 checksum for file."""
+        import hashlib
+
+        print("\n📝 Generating SHA256 checksum...")
+        sha256_hash = hashlib.sha256()
+
+        with open(file_path, "rb") as f:
+            for byte_block in iter(lambda: f.read(4096), b""):
+                sha256_hash.update(byte_block)
+
+        checksum = sha256_hash.hexdigest()
+        checksum_file = file_path.parent / f"{file_path.name}.sha256"
+
+        checksum_file.write_text(checksum)
+        print(f"✅ Checksum generated")
+        print(f"   File: {checksum_file}")
+        print(f"   Hash: {checksum}")
+
     def create_msi(self) -> bool:
         """Create MSI installer using WiX Toolset.