Add release headers service, runtime-aware API header handling, and i18n updates for release configuration

- Implement `releaseHeaders.js` to manage release-related HTTP headers.
- Update requests to include runtime-based release headers.
- Extend i18n phrases across multiple locales for release runtime and configuration labels.
- Enhance unit tests for header building and API availability error handling.

tests/unit/release-timeline.spec.js

@@ -3,6 +3,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import {
   __resetReleaseTimelineForTests,
   __setReleaseTimelineTransportForTests,
+  buildCurrentReleaseHeaders,
   buildReleaseTimelineContext,
   configureReleaseRuntime,
   flushReleaseTimelineEvents,
@@ -54,15 +55,33 @@ describe("release timeline runtime", () => {
         bundle_id: 31,
       },
       urls: {
-        frontend_base_url: "https://lb.truckwash.io/canary/frontend/",
-        api_base_url: "https://lb.truckwash.io/canary/api/",
+        frontend_base_url: "https://api-v2.truckwash.io/canary/frontend/",
+        api_base_url: "https://api-v2.truckwash.io/canary/api/",
       },
     });
 
-    expect(releaseRuntimeState.frontendBaseUrl).toBe("https://lb.truckwash.io/canary/frontend");
-    expect(releaseRuntimeState.apiBaseUrl).toBe("https://lb.truckwash.io/canary/api");
-    expect(getReleaseRuntimeApiBaseUrl()).toBe("https://lb.truckwash.io/canary/api");
-    expect(resolveReleaseApiUrl("/orders")).toBe("https://lb.truckwash.io/canary/api/orders");
+    expect(releaseRuntimeState.frontendBaseUrl).toBe("https://api-v2.truckwash.io/canary/frontend");
+    expect(releaseRuntimeState.apiBaseUrl).toBe("https://api-v2.truckwash.io/canary/api");
+    expect(getReleaseRuntimeApiBaseUrl()).toBe("https://api-v2.truckwash.io/canary/api");
+    expect(resolveReleaseApiUrl("/orders")).toBe("https://api-v2.truckwash.io/canary/api/orders");
+  });
+
+  it("builds release headers from the active runtime state", () => {
+    configureReleaseRuntime({
+      trace_id: "trace-headers",
+      channel: { slug: "internal", name: "Intern" },
+      versions: {
+        frontend: { version_label: "frontend-internal", commit_sha: "130cc2fc106a" },
+        api: { version_label: "api-internal" },
+        bundle_id: 42,
+      },
+    });
+
+    expect(buildCurrentReleaseHeaders()).toMatchObject({
+      "X-Release-Trace": "trace-headers",
+      "X-Release-Channel": "internal",
+      "X-Frontend-Version": "130cc2fc106a",
+    });
   });
 
   it("redacts sensitive payload keys recursively", () => {