feat: WebSearch tri-state, account stats pricing fix, quota cache fix, usage tooltip

WebSearch tri-state switch:
- Account-level web_search_emulation changed from bool to tri-state
  string: "default" (follow channel) / "enabled" / "disabled"
- shouldEmulateWebSearch checks channel config when account is "default"
- SQL migration converts old bool values
- Frontend select replaces toggle in Edit/CreateAccountModal

Account stats pricing:
- resolveAccountStatsCost uses upstream model (post-mapping) for matching
- Priority: custom rules → model pricing file (when toggle on) → default
- Custom rules always configurable, independent of toggle
- Account ID field changed to searchable selector filtered by platform
- Description updated to reflect new behavior

Quota notification cache fix:
- CheckAccountQuotaAfterIncrement fetches real-time account from DB
- Reconstructs pre-increment usage for accurate threshold crossing detection
- New AccountQuotaReader interface (minimal: GetByID only)

Usage tooltip:
- Per-request/image billing shows per-request price instead of $0 token price
- Token billing continues to show input/output price per million tokens

frontend/src/components/account/EditAccountModal.vue

@@ -1161,7 +1161,11 @@
               {{ t('admin.accounts.anthropic.webSearchEmulationDesc') }}
             </p>
           </div>
-          <Toggle v-model="webSearchEmulationEnabled" />
+          <select v-model="webSearchEmulationMode" class="input w-32 text-sm">
+            <option value="default">{{ t('admin.accounts.anthropic.webSearchDefault') }}</option>
+            <option value="enabled">{{ t('admin.accounts.anthropic.webSearchEnabled') }}</option>
+            <option value="disabled">{{ t('admin.accounts.anthropic.webSearchDisabled') }}</option>
+          </select>
         </div>
       </div>
 
@@ -1844,7 +1848,6 @@ import ConfirmDialog from '@/components/common/ConfirmDialog.vue'
 import Select from '@/components/common/Select.vue'
 import Icon from '@/components/icons/Icon.vue'
 import ProxySelector from '@/components/common/ProxySelector.vue'
-import Toggle from '@/components/common/Toggle.vue'
 import GroupSelector from '@/components/common/GroupSelector.vue'
 import ModelWhitelistSelector from '@/components/account/ModelWhitelistSelector.vue'
 import QuotaLimitCard from '@/components/account/QuotaLimitCard.vue'
@@ -1986,7 +1989,7 @@ const openaiOAuthResponsesWebSocketV2Mode = ref<OpenAIWSMode>(OPENAI_WS_MODE_OFF
 const openaiAPIKeyResponsesWebSocketV2Mode = ref<OpenAIWSMode>(OPENAI_WS_MODE_OFF)
 const codexCLIOnlyEnabled = ref(false)
 const anthropicPassthroughEnabled = ref(false)
-const webSearchEmulationEnabled = ref(false)
+const webSearchEmulationMode = ref('default')
 const webSearchGlobalEnabled = ref(false)
 
 // Load web search global state once
@@ -2171,7 +2174,7 @@ const syncFormFromAccount = (newAccount: Account | null) => {
   openaiAPIKeyResponsesWebSocketV2Mode.value = OPENAI_WS_MODE_OFF
   codexCLIOnlyEnabled.value = false
   anthropicPassthroughEnabled.value = false
-  webSearchEmulationEnabled.value = false
+  webSearchEmulationMode.value = 'default'
   if (newAccount.platform === 'openai' && (newAccount.type === 'oauth' || newAccount.type === 'apikey')) {
     openaiPassthroughEnabled.value = extra?.openai_passthrough === true || extra?.openai_oauth_passthrough === true
     openaiOAuthResponsesWebSocketV2Mode.value = resolveOpenAIWSModeFromExtra(extra, {
@@ -2192,7 +2195,15 @@ const syncFormFromAccount = (newAccount: Account | null) => {
   }
   if (newAccount.platform === 'anthropic' && newAccount.type === 'apikey') {
     anthropicPassthroughEnabled.value = extra?.anthropic_passthrough === true
-    webSearchEmulationEnabled.value = extra?.web_search_emulation === true
+    // 三态：string "default"/"enabled"/"disabled"，向后兼容旧 bool
+    const wsVal = extra?.web_search_emulation
+    if (wsVal === 'enabled' || wsVal === 'disabled') {
+      webSearchEmulationMode.value = wsVal
+    } else if (wsVal === true) {
+      webSearchEmulationMode.value = 'enabled'
+    } else {
+      webSearchEmulationMode.value = 'default'
+    }
   }
 
   // Load quota limit for apikey/bedrock accounts (bedrock quota is also loaded in its own branch above)
@@ -3180,10 +3191,10 @@ const handleSubmit = async () => {
       } else {
         delete newExtra.anthropic_passthrough
       }
-      if (webSearchEmulationEnabled.value) {
-        newExtra.web_search_emulation = true
-      } else {
+      if (webSearchEmulationMode.value === 'default') {
         delete newExtra.web_search_emulation
+      } else {
+        newExtra.web_search_emulation = webSearchEmulationMode.value
       }
       updatePayload.extra = newExtra
     }