fix(#411): sanitize Bearer tokens in verifySession logs + warn on non-Error thrown values

- Redact Bearer tokens from error stacks/messages before logging to
  prevent session token leakage into server logs
- Add logger.warn for non-Error thrown values in verifySession catch
  block for observability
- Add tests for token redaction and non-Error warn logging

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/auth/auth.service.spec.ts

@@ -609,5 +609,94 @@ describe("AuthService", () => {
 
       await expect(service.verifySession("any-token")).rejects.toThrow("Database connection lost");
     });
+
+    it("should redact Bearer tokens from logged error messages", async () => {
+      const auth = service.getAuth();
+      const errorWithToken = new Error(
+        "Request failed: Bearer eyJhbGciOiJIUzI1NiJ9.secret-payload in header"
+      );
+      const mockGetSession = vi.fn().mockRejectedValue(errorWithToken);
+      auth.api = { getSession: mockGetSession } as any;
+
+      const loggerError = vi.spyOn(service["logger"], "error");
+
+      await expect(service.verifySession("any-token")).rejects.toThrow();
+
+      expect(loggerError).toHaveBeenCalledWith(
+        "Session verification failed due to unexpected error",
+        expect.stringContaining("Bearer [REDACTED]")
+      );
+      expect(loggerError).toHaveBeenCalledWith(
+        "Session verification failed due to unexpected error",
+        expect.not.stringContaining("eyJhbGciOiJIUzI1NiJ9")
+      );
+    });
+
+    it("should redact Bearer tokens from error stack traces", async () => {
+      const auth = service.getAuth();
+      const errorWithToken = new Error("Something went wrong");
+      errorWithToken.stack =
+        "Error: Something went wrong\n    at fetch (Bearer abc123-secret-token)\n    at verifySession";
+      const mockGetSession = vi.fn().mockRejectedValue(errorWithToken);
+      auth.api = { getSession: mockGetSession } as any;
+
+      const loggerError = vi.spyOn(service["logger"], "error");
+
+      await expect(service.verifySession("any-token")).rejects.toThrow();
+
+      expect(loggerError).toHaveBeenCalledWith(
+        "Session verification failed due to unexpected error",
+        expect.stringContaining("Bearer [REDACTED]")
+      );
+      expect(loggerError).toHaveBeenCalledWith(
+        "Session verification failed due to unexpected error",
+        expect.not.stringContaining("abc123-secret-token")
+      );
+    });
+
+    it("should warn when a non-Error string value is thrown", async () => {
+      const auth = service.getAuth();
+      const mockGetSession = vi.fn().mockRejectedValue("string-error");
+      auth.api = { getSession: mockGetSession } as any;
+
+      const loggerWarn = vi.spyOn(service["logger"], "warn");
+
+      const result = await service.verifySession("any-token");
+
+      expect(result).toBeNull();
+      expect(loggerWarn).toHaveBeenCalledWith(
+        "Session verification received non-Error thrown value",
+        "string-error"
+      );
+    });
+
+    it("should warn with JSON when a non-Error object is thrown", async () => {
+      const auth = service.getAuth();
+      const mockGetSession = vi.fn().mockRejectedValue({ code: "ERR_UNKNOWN" });
+      auth.api = { getSession: mockGetSession } as any;
+
+      const loggerWarn = vi.spyOn(service["logger"], "warn");
+
+      const result = await service.verifySession("any-token");
+
+      expect(result).toBeNull();
+      expect(loggerWarn).toHaveBeenCalledWith(
+        "Session verification received non-Error thrown value",
+        JSON.stringify({ code: "ERR_UNKNOWN" })
+      );
+    });
+
+    it("should not warn for expected auth errors (Error instances)", async () => {
+      const auth = service.getAuth();
+      const mockGetSession = vi.fn().mockRejectedValue(new Error("Invalid token provided"));
+      auth.api = { getSession: mockGetSession } as any;
+
+      const loggerWarn = vi.spyOn(service["logger"], "warn");
+
+      const result = await service.verifySession("bad-token");
+
+      expect(result).toBeNull();
+      expect(loggerWarn).not.toHaveBeenCalled();
+    });
   });
 });