feat(config): 统一加载 .env 并强化本地启动脚本

scripts/start-local.ps1

@@ -103,11 +103,9 @@ $dataDirLiteral = ConvertTo-PowerShellLiteral $dataDir
 $backendCommand = @"
 `$ErrorActionPreference = 'Stop'
 Set-Location -LiteralPath $backendDirLiteral
-`$env:CANVAS_BACKEND_ADDR = '127.0.0.1:7381'
-`$env:CANVAS_BACKEND_DATA_DIR = $dataDirLiteral
 `$env:GOCACHE = $(ConvertTo-PowerShellLiteral $goBuildCache)
 `$env:GOMODCACHE = $(ConvertTo-PowerShellLiteral $goModuleCache)
-Write-Host '影策后端：http://127.0.0.1:7381' -ForegroundColor Cyan
+Write-Host "影策后端：$($env:CANVAS_BACKEND_ADDR)" -ForegroundColor Cyan
 go run ./cmd/server
 "@