fix: an unknown redirect status, match or query is refused, not defaulted (WR-17)

The API, MCP, batches and the CSV import copied any value and Normalize
replaced it with the default, answering 201 for a 307 saved as a 301.
RedirectFields.Problems refuses values outside {301, 302, 410}, {exact,
pattern, regex} and {ignore, pass} with value_invalid; the import marks
such rows refused.

batch_test.go

@@ -126,6 +126,12 @@ func TestBatch(t *testing.T) {
 	if after := env.snapshot(t); after != before {
 		t.Fatalf("a refused batch wrote:\n%s", after)
 	}
+	coerced := env.mcp(t, http.MethodPost, "/_seo/api/v1/batch", agent, map[string]any{"changes": []any{
+		map[string]any{"op": "create_redirect", "redirect": map[string]any{"source": "/s307", "target": "/pages/a", "status": 307}},
+	}})
+	if coerced.Code != http.StatusUnprocessableEntity || !strings.Contains(coerced.Body.String(), `"status"`) {
+		t.Fatalf("batch with status 307 = %d %s, want 422 on status", coerced.Code, coerced.Body.String())
+	}
 	if rec := env.mcp(t, http.MethodPost, "/_seo/api/v1/batch", agent, map[string]any{"changes": []any{map[string]any{"op": "explode"}}}); rec.Code != http.StatusUnprocessableEntity {
 		t.Fatalf("unknown op = %d, want 422", rec.Code)
 	}