fix(api): add refreshable: true to claude OAuth test config

Claude OAuth tokens are short-lived and require refresh. The runtime
HealthCheck (open-sse) already refreshes them successfully, but the
Dashboard test endpoint was missing `refreshable: true` in its config.

This caused the Dashboard to show "auth failed / Token expired" for
Claude providers even though the tokens were being refreshed correctly
at runtime. The codex provider already had this flag set.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/app/api/providers/[id]/test/route.ts

@@ -20,6 +20,7 @@ const OAUTH_TEST_CONFIG = {
   claude: {
     // Claude doesn't have userinfo, we verify token exists and not expired
     checkExpiry: true,
+    refreshable: true,
   },
   codex: {
     // Codex OAuth tokens are ChatGPT session tokens, NOT standard OpenAI API keys.