test(response): fix AbortWithError router tests and oauth/bootstrap reliability

- Add middleware_test.go covering ErrorHandlerMiddleware and Abort helpers
- Switch router test setups to testhelper.NewTestGinEngine for error JSON
- Fix OAuth provider cache to use mock HTTP client and normalize issuer URLs
- Add ResetInitRuntimeOnceForTest to make bootstrap tests hermetic under -count
- Update admin/task test imports for upload/task package move

internal/bootstrap/bootstrap.go

@@ -85,4 +85,9 @@ func Init(ctx context.Context, opts Options) {
 			risk_control.InitLogWriter(ctx)
 		}
 	})
+}
+
+// ResetInitRuntimeOnceForTest clears initRuntimeOnce so Init can run again in unit tests.
+func ResetInitRuntimeOnceForTest() {
+	initRuntimeOnce = sync.Once{}
 }