test(api): achieve 100% coverage across all routes, middleware, and services

- Add full test suite for frontend.ts (POST /log and POST /error)
- Add error-path tests to all route handlers to cover catch blocks
  triggered by Prisma rejections
- Add non-Error throw tests to cover the `new Error(String(error))`
  ternary false branch in middleware, services, and route catch handlers
- Suppress unreachable outer catch in about.ts with v8 ignore (fetchReleases
  swallows all errors internally, making the outer catch genuinely dead code)

apps/api/test/services/discord.spec.ts

@@ -86,5 +86,22 @@ describe("discord service", () => {
       expect(result.id).toBe("123");
       expect(result.username).toBe("testuser");
     });
+
+    it("re-throws when fetch rejects with a non-Error value", async () => {
+      mockFetch.mockRejectedValueOnce("raw string error");
+      const { fetchDiscordUser } = await import("../../src/services/discord.js");
+      await expect(fetchDiscordUser("some_token")).rejects.toBe("raw string error");
+    });
+  });
+
+  describe("exchangeCode non-Error throw", () => {
+    it("re-throws when fetch rejects with a non-Error value", async () => {
+      process.env["DISCORD_CLIENT_ID"] = "cid";
+      process.env["DISCORD_CLIENT_SECRET"] = "secret";
+      process.env["DISCORD_REDIRECT_URI"] = "http://localhost/cb";
+      mockFetch.mockRejectedValueOnce("raw string error");
+      const { exchangeCode } = await import("../../src/services/discord.js");
+      await expect(exchangeCode("some_code")).rejects.toBe("raw string error");
+    });
   });
 });