refactor: optimize middleware with pure ASGI implementation and enhance security measures

- Replace BaseHTTPMiddleware with pure ASGI implementation in plugin middleware for better streaming response handling
- Add trusted proxy count configuration for client IP extraction in reverse proxy environments
- Implement audit log cleanup scheduler with configurable retention period
- Replace plaintext token logging with SHA256 hash fingerprints for security
- Fix database session lifecycle management in middleware
- Improve request tracing and error logging throughout the system
- Add comprehensive tests for pipeline architecture

frontend/src/features/api-keys/components/StandaloneKeyFormDialog.vue

@@ -132,7 +132,7 @@
               type="number"
               min="1"
               max="10000"
-              placeholder="100"
+              placeholder="留空不限制"
               class="h-10"
               @update:model-value="(v) => form.rate_limit = parseNumberInput(v, { min: 1, max: 10000 })"
             />
@@ -376,7 +376,7 @@ const form = ref<StandaloneKeyFormData>({
   initial_balance_usd: 10,
   expire_days: undefined,
   never_expire: true,
-  rate_limit: 100,
+  rate_limit: undefined,
   auto_delete_on_expiry: false,
   allowed_providers: [],
   allowed_api_formats: [],
@@ -389,7 +389,7 @@ function resetForm() {
     initial_balance_usd: 10,
     expire_days: undefined,
     never_expire: true,
-    rate_limit: 100,
+    rate_limit: undefined,
     auto_delete_on_expiry: false,
     allowed_providers: [],
     allowed_api_formats: [],
@@ -408,7 +408,7 @@ function loadKeyData() {
     initial_balance_usd: props.apiKey.initial_balance_usd,
     expire_days: props.apiKey.expire_days,
     never_expire: props.apiKey.never_expire,
-    rate_limit: props.apiKey.rate_limit || 100,
+    rate_limit: props.apiKey.rate_limit,
     auto_delete_on_expiry: props.apiKey.auto_delete_on_expiry,
     allowed_providers: props.apiKey.allowed_providers || [],
     allowed_api_formats: props.apiKey.allowed_api_formats || [],

frontend/src/features/usage/components/RequestDetailDrawer.vue

@@ -25,7 +25,7 @@
                 </h3>
                 <div class="flex items-center gap-1 text-sm font-mono text-muted-foreground bg-muted px-2 py-0.5 rounded">
                   <span>{{ detail?.model || '-' }}</span>
-                  <template v-if="detail?.target_model">
+                  <template v-if="detail?.target_model && detail.target_model !== detail.model">
                     <svg
                       xmlns="http://www.w3.org/2000/svg"
                       viewBox="0 0 20 20"