fix: miscellaneous quick fixes from CodeRabbit review

- log_info_generate.go: add nil guard in InjectTieredBillingInfo
- billing_expr_request.go: merge headers instead of replacing
- go.mod: remove incorrect // indirect on expr-lang/expr
- ToolPriceSettings.jsx: add null check in syncToVisual
- tool_billing.go: fix PricePer1K for image_generation (per-call, not per-1K)
- utils.jsx: add minute() to time condition regex
- useUsageLogsData.jsx: pass displayMode to renderTieredModelPrice
- AGENTS.md, CLAUDE.md: fix Rule 6/7 ordering
- relay-gemini.go: add TEXT modality case in CandidatesTokensDetails

web/src/pages/Setting/Ratio/ToolPriceSettings.jsx

@@ -102,7 +102,7 @@ export default function ToolPriceSettings({ options }) {
     setJsonText(text);
     try {
       const parsed = JSON.parse(text);
-      if (typeof parsed !== 'object' || Array.isArray(parsed)) {
+      if (typeof parsed !== 'object' || Array.isArray(parsed) || parsed === null) {
         setJsonError(t('JSON 必须是对象'));
         return;
       }