test: 添加用于诊断环境变量加载的测试脚本

添加诊断脚本 test_config.py，用于测试和验证环境变量配置的正确加载。
脚本检查当前工作目录、Python 环境、.env 文件位置、已加载的环境变量，
并测试 python-dotenv 和 pydantic-settings 的集成情况，以协助调试配置问题。

test_config.py

@@ -0,0 +1,104 @@
+"""Diagnostic script to test environment variable loading."""
+import os
+import sys
+from pathlib import Path
+
+# Set UTF-8 encoding for Windows console
+if sys.platform == "win32":
+    import codecs
+    sys.stdout = codecs.getwriter("utf-8")(sys.stdout.buffer, "strict")
+    sys.stderr = codecs.getwriter("utf-8")(sys.stderr.buffer, "strict")
+
+print("=" * 60)
+print("Config Diagnostic Script")
+print("=" * 60)
+
+# Check current directory
+print(f"\n1. Current working directory: {os.getcwd()}")
+
+# Check Python path
+print(f"\n2. Python executable: {sys.executable}")
+print(f"   Python version: {sys.version}")
+
+# Check if we're running from backend directory
+in_backend = Path.cwd().name == "backend"
+print(f"\n3. Running from backend directory: {in_backend}")
+
+# Check .env file location
+env_paths = [
+    Path(".env"),
+    Path("../.env"),
+    Path.cwd().parent / ".env",
+    Path("C:/electron/git/.env")
+]
+
+print(f"\n4. Looking for .env file:")
+for p in env_paths:
+    exists = p.exists()
+    if exists:
+        print(f"   ✓ FOUND: {p}")
+        # Show first few lines
+        with open(p, 'r', encoding='utf-8') as f:
+            lines = f.readlines()[:3]
+            print(f"     Content preview:")
+            for line in lines:
+                print(f"       {line.rstrip()}")
+    else:
+        print(f"   ✗ NOT FOUND: {p}")
+
+# Check environment variables
+print(f"\n5. Environment variables starting with 'GM_':")
+gm_vars = {k: v for k, v in os.environ.items() if k.startswith('GM_')}
+if gm_vars:
+    for k, v in gm_vars.items():
+        # Truncate long values for display
+        display_v = v[:30] + "..." if len(v) > 30 else v
+        print(f"   {k} = {display_v}")
+else:
+    print("   (none found)")
+
+# Try python-dotenv if available
+print(f"\n6. Testing python-dotenv:")
+try:
+    from dotenv import load_dotenv
+    print("   python-dotenv is installed")
+
+    # Try loading from different paths
+    for env_path in env_paths:
+        if env_path.exists():
+            result = load_dotenv(env_path, override=True)
+            print(f"   load_dotenv({env_path.name}): loaded {result} variables")
+            # Check what got loaded
+            after_vars = {k: v for k, v in os.environ.items() if k.startswith('GM_')}
+            print(f"   GM_ vars after load: {len(after_vars)}")
+            break
+except ImportError:
+    print("   python-dotenv NOT installed")
+
+# Try importing pydantic-settings
+print(f"\n7. Testing pydantic-settings:")
+try:
+    from pydantic_settings import BaseSettings, SettingsConfigDict
+    print("   pydantic-settings is installed")
+
+    class TestSettings(BaseSettings):
+        model_config = SettingsConfigDict(
+            env_prefix='GM_',
+            env_file='.env',
+            env_file_encoding='utf-8',
+        )
+        encrypt_key: str = "default"
+        api_token: str = "default"
+
+    try:
+        s = TestSettings()
+        print(f"   ✓ Settings loaded successfully")
+        print(f"   encrypt_key: {s.encrypt_key[:20]}...")
+        print(f"   api_token: {s.api_token[:20]}...")
+    except Exception as e:
+        print(f"   ✗ Settings failed: {type(e).__name__}: {e}")
+
+except ImportError as e:
+    print(f"   pydantic-settings NOT installed: {e}")
+
+print("\n" + "=" * 60)