feat: complete remaining Go backend modules

tests/usage-http-contract.test.ts

@@ -0,0 +1,15 @@
+import { readFile } from "node:fs/promises";
+import { describe, expect, it } from "vitest";
+
+describe("usage HTTP compatibility fixture", () => {
+  it("freezes personal/admin scope and filters", async () => {
+    const fixture = JSON.parse(await readFile("contracts/usage/http-v1.json", "utf8"));
+    expect(fixture).toMatchObject({
+      version: 1,
+      presets: ["today", "7d", "30d", "month"],
+      capabilities: ["image.generate", "video.generate"],
+      infrastructureStatus: 500
+    });
+    expect(fixture.routes).toContainEqual(expect.objectContaining({ path: "/api/admin/usage", requirement: "admin", organizationAdminScope: "refreshed_session" }));
+  });
+});