feat(CI): 添加Flutter安装脚本并改进Windows构建流程

添加install_flutter_simple.bat脚本用于在Windows上自动安装Flutter
改进docker.yml中的Windows构建步骤，增加Flutter路径检测和powershell支持

.gitea/workflows/docker.yml

@@ -189,19 +189,51 @@ jobs:
         }
 
     - name: Enable Windows desktop
-      run: flutter config --enable-windows-desktop
+      shell: powershell
+      run: |
+        $flutterPath = Get-Command flutter -ErrorAction SilentlyContinue
+        if (-not $flutterPath) {
+          Write-Host "Flutter not found, checking common locations..."
+          $commonPaths = @(
+            "C:\flutter\bin\flutter.exe",
+            "C:\tools\flutter\bin\flutter.exe",
+            "${env:USERPROFILE}\flutter\bin\flutter.exe"
+          )
+          $flutterFound = $false
+          foreach ($path in $commonPaths) {
+            if (Test-Path $path) {
+              Write-Host "Found Flutter at: $path"
+              $env:PATH = "$(Split-Path $path);$env:PATH"
+              $flutterFound = $true
+              break
+            }
+          }
+          if (-not $flutterFound) {
+            Write-Host "ERROR: Flutter not found. Please install Flutter first."
+            exit 1
+          }
+        }
+        flutter config --enable-windows-desktop
 
     - name: Get dependencies
-      run: flutter pub get
+      shell: powershell  
+      run: |
+        flutter pub get
 
     - name: Generate code
-      run: dart run build_runner build --delete-conflicting-outputs
+      shell: powershell
+      run: |
+        dart run build_runner build --delete-conflicting-outputs
 
     - name: Build Windows Debug
-      run: flutter build windows
+      shell: powershell
+      run: |
+        flutter build windows
 
     - name: Build Windows Release
-      run: flutter build windows --release
+      shell: powershell
+      run: |
+        flutter build windows --release
 
     - name: Upload Debug build artifacts
       uses: actions/upload-artifact@v3