feat(tool-configs): add frontend tool config management page

- Create ToolConfigsPage with tool type selector, config list, and add/edit form
- Support both env and file config types
- Add route /tool-configs and navigation item
- Update API client with tool config endpoints
- Build passes successfully

apps/web/src/components/app-shell.tsx

@@ -15,6 +15,7 @@ const NAV_ITEMS: { to: string; label: string; icon: IconName }[] = [
   { to: "/projects", label: "Projects", icon: "projects" },
   { to: "/ssh-keys", label: "SSH Keys", icon: "profile" },
   { to: "/tool-types", label: "Tool Types", icon: "code" },
+  { to: "/tool-configs", label: "Tool Configs", icon: "settings" },
   { to: "/settings", label: "Settings", icon: "settings" }
 ];