feat(multimodal): 实现本地模型管线与请求用量配置

backend/scripts/install-model-runtime.ps1

@@ -0,0 +1,19 @@
+param(
+    [ValidateSet('cpu', 'cuda')][string]$Device = 'cpu'
+)
+$ErrorActionPreference = 'Stop'
+$backendRoot = Split-Path $PSScriptRoot -Parent
+$runtimeRoot = Join-Path $backendRoot '.venv-models'
+$runtimePython = Join-Path $runtimeRoot 'Scripts/python.exe'
+if (!(Test-Path -LiteralPath $runtimePython)) {
+    & uv venv --python 3.12 $runtimeRoot
+    if ($LASTEXITCODE -ne 0) { throw '无法创建模型运行环境' }
+}
+# CPU is the default. CUDA wheels include the runtime, not the NVIDIA driver.
+$torchIndex = if ($Device -eq 'cuda') { 'https://download.pytorch.org/whl/cu128' } else { 'https://download.pytorch.org/whl/cpu' }
+& uv pip install --python $runtimePython --index-url $torchIndex 'torch==2.9.1' 'torchaudio==2.9.1'
+if ($LASTEXITCODE -ne 0) { throw 'PyTorch 安装失败' }
+& uv pip install --python $runtimePython -r (Join-Path $PSScriptRoot 'model-requirements.lock') -c (Join-Path $PSScriptRoot 'model-requirements.txt')
+if ($LASTEXITCODE -ne 0) { throw '模型依赖安装失败' }
+& $runtimePython -c 'import torch; print({"torch":torch.__version__,"cuda_available":torch.cuda.is_available()})'
+if ($LASTEXITCODE -ne 0) { throw '模型运行环境检查失败' }