feat: add provider-specific terminal button

Add a terminal button next to each provider card that opens a new terminal
window with that provider's specific API configuration. This allows using
different providers independently without changing the global setting.

Changes:
- Backend: Add `open_provider_terminal` command that extracts provider
  config and creates a temporary claude settings file
- Frontend: Add terminal button to provider cards with proper callback
  propagation through component hierarchy
- Support macOS (Terminal.app), Linux (gnome-terminal, konsole, etc.),
  and Windows (cmd)

Each provider gets a unique config file named `claude_<providerId>_<pid>.json`
in the temp directory, containing the provider's API configuration.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/providers/ProviderCard.tsx

@@ -33,6 +33,7 @@ interface ProviderCardProps {
   onOpenWebsite: (url: string) => void;
   onDuplicate: (provider: Provider) => void;
   onTest?: (provider: Provider) => void;
+  onOpenTerminal?: (provider: Provider) => void;
   isTesting?: boolean;
   isProxyRunning: boolean;
   isProxyTakeover?: boolean; // 代理接管模式（Live配置已被接管，切换为热切换）
@@ -91,6 +92,7 @@ export function ProviderCard({
   onOpenWebsite,
   onDuplicate,
   onTest,
+  onOpenTerminal,
   isTesting,
   isProxyRunning,
   isProxyTakeover = false,
@@ -339,6 +341,7 @@ export function ProviderCard({
               onTest={onTest ? () => onTest(provider) : undefined}
               onConfigureUsage={() => onConfigureUsage(provider)}
               onDelete={() => onDelete(provider)}
+              onOpenTerminal={onOpenTerminal ? () => onOpenTerminal(provider) : undefined}
               // 故障转移相关
               isAutoFailoverEnabled={isAutoFailoverEnabled}
               isInFailoverQueue={isInFailoverQueue}