feat(usage): add Kimi and DeepSeek usage handlers

Wire /v1/usages for Kimi (OAuth + API key) and balance API for DeepSeek,
flag both providers with usage/usageApikey, and normalize their quotas
in the dashboard ProviderLimits parser.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/unit/deepseek-usage.test.js

@@ -0,0 +1,149 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+vi.mock("../../open-sse/utils/proxyFetch.js", () => ({
+  proxyAwareFetch: vi.fn(),
+}));
+
+import { proxyAwareFetch } from "../../open-sse/utils/proxyFetch.js";
+import { getUsageForProvider } from "../../open-sse/services/usage.js";
+import {
+  USAGE_SUPPORTED_PROVIDERS,
+  USAGE_APIKEY_PROVIDERS,
+} from "../../src/shared/constants/providers.js";
+import { parseQuotaData } from "../../src/app/(dashboard)/dashboard/usage/components/ProviderLimits/utils.js";
+
+const BALANCE_URL = "https://api.deepseek.com/user/balance";
+
+function jsonResponse(body, status = 200) {
+  return new Response(JSON.stringify(body), {
+    status,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+const ACTIVE_BALANCE = {
+  is_available: true,
+  balance_infos: [
+    {
+      currency: "USD",
+      total_balance: "12.50",
+      granted_balance: "2.50",
+      topped_up_balance: "10.00",
+    },
+    {
+      currency: "CNY",
+      total_balance: "0.00",
+      granted_balance: "0.00",
+      topped_up_balance: "0.00",
+    },
+  ],
+};
+
+describe("deepseek registry usage flags", () => {
+  it("is listed for apikey quota dashboard", () => {
+    expect(USAGE_SUPPORTED_PROVIDERS).toContain("deepseek");
+    expect(USAGE_APIKEY_PROVIDERS).toContain("deepseek");
+  });
+});
+
+describe("getUsageForProvider(deepseek)", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("GETs /user/balance with Bearer apiKey", async () => {
+    proxyAwareFetch.mockResolvedValueOnce(jsonResponse(ACTIVE_BALANCE));
+
+    const usage = await getUsageForProvider({
+      provider: "deepseek",
+      apiKey: "sk-ds-test",
+    });
+
+    expect(usage.message).toBeUndefined();
+    expect(usage.plan).toBe("DeepSeek");
+    expect(proxyAwareFetch).toHaveBeenCalledTimes(1);
+    const [url, opts] = proxyAwareFetch.mock.calls[0];
+    expect(url).toBe(BALANCE_URL);
+    expect(opts.method).toBe("GET");
+    expect(opts.headers.Authorization).toBe("Bearer sk-ds-test");
+  });
+
+  it("maps balances without absolute remaining (UI treats remaining as %)", async () => {
+    proxyAwareFetch.mockResolvedValueOnce(jsonResponse(ACTIVE_BALANCE));
+
+    const usage = await getUsageForProvider({
+      provider: "deepseek",
+      apiKey: "sk-ds-test",
+    });
+
+    expect(usage.quotas["Balance (USD)"]).toMatchObject({
+      used: 0,
+      total: 12.5,
+      remainingPercentage: 100,
+    });
+    expect(usage.quotas["Balance (USD)"].remaining).toBeUndefined();
+    // Zero CNY still listed so user sees currency row
+    expect(usage.quotas["Balance (CNY)"]).toMatchObject({
+      used: 0,
+      total: 0,
+      remainingPercentage: 0,
+    });
+  });
+
+  it("marks plan unavailable when is_available false", async () => {
+    proxyAwareFetch.mockResolvedValueOnce(
+      jsonResponse({
+        is_available: false,
+        balance_infos: [
+          {
+            currency: "USD",
+            total_balance: "0",
+            granted_balance: "0",
+            topped_up_balance: "0",
+          },
+        ],
+      }),
+    );
+
+    const usage = await getUsageForProvider({
+      provider: "deepseek",
+      apiKey: "sk-ds-test",
+    });
+
+    expect(usage.plan).toMatch(/insufficient|unavailable/i);
+    expect(usage.quotas["Balance (USD)"].remainingPercentage).toBe(0);
+  });
+
+  it("returns message on missing key / 401", async () => {
+    const missing = await getUsageForProvider({ provider: "deepseek" });
+    expect(missing.message).toMatch(/api key/i);
+    expect(proxyAwareFetch).not.toHaveBeenCalled();
+
+    proxyAwareFetch.mockResolvedValueOnce(jsonResponse({ error: "no" }, 401));
+    const auth = await getUsageForProvider({
+      provider: "deepseek",
+      apiKey: "bad",
+    });
+    expect(auth.message).toMatch(/auth|key|401/i);
+  });
+});
+
+describe("parseQuotaData(deepseek)", () => {
+  it("forwards remainingPercentage for balance rows", () => {
+    const rows = parseQuotaData("deepseek", {
+      plan: "DeepSeek",
+      quotas: {
+        "Balance (USD)": {
+          used: 0,
+          total: 12.5,
+          remainingPercentage: 100,
+        },
+      },
+    });
+    expect(rows[0]).toMatchObject({
+      name: "Balance (USD)",
+      total: 12.5,
+      remainingPercentage: 100,
+    });
+  });
+});