fix: address load_factor code review findings

- Fix bulk edit: send 0 instead of null/NaN to clear load_factor
- Fix edit modal: explicit NaN check instead of implicit falsy
- Fix create modal: use ?? instead of || for load_factor
- Add load_factor upper limit validation (max 10000)
- Add //go:build unit tag and self-contained intPtrHelper in test
- Add design intent comments on WaitPlan.MaxConcurrency

frontend/src/components/account/BulkEditAccountModal.vue

@@ -1227,7 +1227,9 @@ const buildUpdatePayload = (): Record<string, unknown> | null => {
   }
 
   if (enableLoadFactor.value) {
-    updates.load_factor = loadFactor.value
+    // 空值/NaN/0 时发送 0（后端约定 <= 0 表示清除）
+    const lf = loadFactor.value
+    updates.load_factor = (lf != null && !Number.isNaN(lf) && lf > 0) ? lf : 0
   }
 
   if (enablePriority.value) {

frontend/src/components/account/CreateAccountModal.vue

@@ -3491,7 +3491,7 @@ const handleImportAccessToken = async (accessTokenInput: string) => {
           extra: soraExtra,
           proxy_id: form.proxy_id,
           concurrency: form.concurrency,
-          load_factor: form.load_factor || undefined,
+          load_factor: form.load_factor ?? undefined,
           priority: form.priority,
           rate_multiplier: form.rate_multiplier,
           group_ids: form.group_ids,
@@ -3551,7 +3551,7 @@ const createAccountAndFinish = async (
     extra,
     proxy_id: form.proxy_id,
     concurrency: form.concurrency,
-    load_factor: form.load_factor || undefined,
+    load_factor: form.load_factor ?? undefined,
     priority: form.priority,
     rate_multiplier: form.rate_multiplier,
     group_ids: form.group_ids,
@@ -3607,7 +3607,7 @@ const handleOpenAIExchange = async (authCode: string) => {
         extra,
         proxy_id: form.proxy_id,
         concurrency: form.concurrency,
-        load_factor: form.load_factor || undefined,
+        load_factor: form.load_factor ?? undefined,
         priority: form.priority,
         rate_multiplier: form.rate_multiplier,
         group_ids: form.group_ids,
@@ -3637,7 +3637,7 @@ const handleOpenAIExchange = async (authCode: string) => {
         extra: soraExtra,
         proxy_id: form.proxy_id,
         concurrency: form.concurrency,
-        load_factor: form.load_factor || undefined,
+        load_factor: form.load_factor ?? undefined,
         priority: form.priority,
         rate_multiplier: form.rate_multiplier,
         group_ids: form.group_ids,
@@ -3715,7 +3715,7 @@ const handleOpenAIValidateRT = async (refreshTokenInput: string) => {
             extra,
             proxy_id: form.proxy_id,
             concurrency: form.concurrency,
-            load_factor: form.load_factor || undefined,
+            load_factor: form.load_factor ?? undefined,
             priority: form.priority,
             rate_multiplier: form.rate_multiplier,
             group_ids: form.group_ids,
@@ -3743,7 +3743,7 @@ const handleOpenAIValidateRT = async (refreshTokenInput: string) => {
             extra: soraExtra,
             proxy_id: form.proxy_id,
             concurrency: form.concurrency,
-            load_factor: form.load_factor || undefined,
+            load_factor: form.load_factor ?? undefined,
             priority: form.priority,
             rate_multiplier: form.rate_multiplier,
             group_ids: form.group_ids,
@@ -3832,7 +3832,7 @@ const handleSoraValidateST = async (sessionTokenInput: string) => {
           extra: soraExtra,
           proxy_id: form.proxy_id,
           concurrency: form.concurrency,
-          load_factor: form.load_factor || undefined,
+          load_factor: form.load_factor ?? undefined,
           priority: form.priority,
           rate_multiplier: form.rate_multiplier,
           group_ids: form.group_ids,
@@ -3921,7 +3921,7 @@ const handleAntigravityValidateRT = async (refreshTokenInput: string) => {
           extra: {},
           proxy_id: form.proxy_id,
           concurrency: form.concurrency,
-          load_factor: form.load_factor || undefined,
+          load_factor: form.load_factor ?? undefined,
           priority: form.priority,
           rate_multiplier: form.rate_multiplier,
           group_ids: form.group_ids,
@@ -4245,7 +4245,7 @@ const handleCookieAuth = async (sessionKey: string) => {
           extra,
           proxy_id: form.proxy_id,
           concurrency: form.concurrency,
-          load_factor: form.load_factor || undefined,
+          load_factor: form.load_factor ?? undefined,
           priority: form.priority,
           rate_multiplier: form.rate_multiplier,
           group_ids: form.group_ids,

frontend/src/components/account/EditAccountModal.vue

@@ -2064,8 +2064,9 @@ const handleSubmit = async () => {
     if (form.expires_at === null) {
       updatePayload.expires_at = 0
     }
-    // load_factor: 空值/0/NaN 时发送 0（后端约定 0 = 清除）
-    if (!form.load_factor || form.load_factor <= 0) {
+    // load_factor: 空值/NaN/0/负数 时发送 0（后端约定 <= 0 = 清除）
+    const lf = form.load_factor
+    if (lf == null || Number.isNaN(lf) || lf <= 0) {
       updatePayload.load_factor = 0
     }
     updatePayload.auto_pause_on_expired = autoPauseOnExpired.value