feat(i18n): add Lingui runtime and development tooling

- add SSR-safe I18nProvider, Translate, locale hooks, catalog activation, and typed runtime APIs

- add consumer-owned Lingui configuration helpers and a CLI for locale creation, extraction, compilation, and project discovery

- add catalog read/write services plus a Vite development API plugin scoped to each consuming application

- add the portal-based I18nDevtool, message editor, dark-theme tracking, and standalone Message Studio

- document the consumer workflow and cover runtime, configuration, catalog, CLI, and Devtool behavior with tests

packages/i18n/src/devtool/app/app.tsx

@@ -0,0 +1,58 @@
+import * as React from "react"
+
+import type { I18nProjectConfig } from "../../config/lingui-config"
+import { I18nProvider } from "../../runtime"
+import { requestDevtoolJson } from "../api-client"
+import { I18nDevtool } from "../i18n-devtool"
+
+type ProjectState =
+  | { status: "loading" }
+  | { error: Error; status: "error" }
+  | { project: I18nProjectConfig; status: "ready" }
+
+export function DevtoolApp() {
+  const [state, setState] = React.useState<ProjectState>({ status: "loading" })
+
+  React.useEffect(() => {
+    requestDevtoolJson<I18nProjectConfig>("/__i18n/project").then(
+      (project) => setState({ project, status: "ready" }),
+      (reason) =>
+        setState({
+          error:
+            reason instanceof Error
+              ? reason
+              : new Error("Unable to load the i18n project."),
+          status: "error",
+        })
+    )
+  }, [])
+
+  if (state.status !== "ready") {
+    return (
+      <main
+        className="devtool-app__state"
+        role={state.status === "error" ? "alert" : "status"}
+      >
+        {state.status === "error"
+          ? state.error.message
+          : "Loading I18n Devtool…"}
+      </main>
+    )
+  }
+
+  const locale = state.project.locales[0]
+
+  if (!locale) {
+    return (
+      <main className="devtool-app__state">
+        Add a locale with <code>workspace-i18n new &lt;locale&gt;</code>.
+      </main>
+    )
+  }
+
+  return (
+    <I18nProvider locale={locale} locales={state.project.locales}>
+      <I18nDevtool defaultOpen mode="standalone" />
+    </I18nProvider>
+  )
+}