fix(desktop): add windows dll search paths for bundled runtime

Author: zouyonghe

desktop/scripts/templates/launch_backend.py

@@ -1,11 +1,55 @@
 from __future__ import annotations
 
+import os
 import runpy
 import sys
 from pathlib import Path
 
 BACKEND_DIR = Path(__file__).resolve().parent
 APP_DIR = BACKEND_DIR / "app"
+_WINDOWS_DLL_DIRECTORY_HANDLES: list[object] = []
+
+
+def configure_windows_dll_search_path() -> None:
+    if sys.platform != "win32" or not hasattr(os, "add_dll_directory"):
+        return
+
+    runtime_executable_dir = Path(sys.executable).resolve().parent
+    candidates = [
+        runtime_executable_dir,
+        runtime_executable_dir / "DLLs",
+        BACKEND_DIR / "python",
+        BACKEND_DIR / "python" / "DLLs",
+    ]
+
+    normalized_added: set[str] = set()
+    path_entries: list[str] = []
+    for candidate in candidates:
+        if not candidate.is_dir():
+            continue
+        candidate_str = str(candidate)
+        candidate_key = candidate_str.lower()
+        if candidate_key in normalized_added:
+            continue
+        normalized_added.add(candidate_key)
+        path_entries.append(candidate_str)
+        try:
+            _WINDOWS_DLL_DIRECTORY_HANDLES.append(
+                os.add_dll_directory(candidate_str),
+            )
+        except OSError:
+            continue
+
+    if path_entries:
+        existing_path = os.environ.get("PATH", "")
+        os.environ["PATH"] = (
+            ";".join(path_entries + [existing_path])
+            if existing_path
+            else ";".join(path_entries)
+        )
+
+
+configure_windows_dll_search_path()
 
 sys.path.insert(0, str(APP_DIR))