fix(notifications): record a relay refusal at warn, not error

A 502 from a channel test reports the user's relay or mail setup, not a fault on this server, yet the status alone raised every press to an error-level event. The event builder gains a ceiling for the status-derived level, and the test routes cap it at warn on the 502 path. The 500 for an unnamed failure stays at error, and explicit elevations are unaffected.

The notifications guide notes that a reverse proxy which replaces 5xx pages hides the detail, so the card falls back to Test failed.

Refs #947

src/app/api/settings/__tests__/private-origin-routes.test.ts

@@ -52,7 +52,10 @@ vi.mock("@/lib/auth/session", () => ({ getSession: vi.fn() }));
 vi.mock("@/lib/auth/audit", () => ({
   auditLog: vi.fn().mockResolvedValue(undefined),
 }));
-vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+const emitIfSampledMock = vi.fn();
+vi.mock("@/lib/logging/transports", () => ({
+  emitIfSampled: (...args: unknown[]) => emitIfSampledMock(...args),
+}));
 vi.mock("@/lib/db-compat", () => ({
   ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
 }));
@@ -374,6 +377,10 @@ describe("POST /api/settings/{webhook,ntfy}/test — the refusal names itself",
         upstreamBody: '{"error":"Bad Request","errorCode":400}',
       });
       expect(json.error).toContain("HTTP 400");
+      // A user's relay refusing is not an operator error: the event is warn.
+      expect(emitIfSampledMock).toHaveBeenCalledWith(
+        expect.objectContaining({ level: "warn" }),
+      );
     },
   );
 
@@ -444,6 +451,9 @@ describe("POST /api/settings/{webhook,ntfy}/test — the refusal names itself",
       expect(response.status).toBe(500);
       const json = await response.json();
       expect(json.meta).toBeUndefined();
+      expect(emitIfSampledMock).toHaveBeenCalledWith(
+        expect.objectContaining({ level: "error" }),
+      );
     },
   );