fix(安全): CSP 策略添加 Google Fonts 支持

在 style-src 中添加 fonts.googleapis.com，在 font-src 中添加
fonts.gstatic.com，解决浏览器控制台因 CSP 策略阻止加载
Google Fonts 样式表的错误。

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/internal/config/config.go

@@ -17,7 +17,7 @@ const (
 	RunModeSimple   = "simple"
 )
 
-const DefaultCSPPolicy = "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' data:; connect-src 'self' https:; frame-ancestors 'none'; base-uri 'self'; form-action 'self'"
+const DefaultCSPPolicy = "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: https:; font-src 'self' data: https://fonts.gstatic.com; connect-src 'self' https:; frame-ancestors 'none'; base-uri 'self'; form-action 'self'"
 
 // 连接池隔离策略常量
 // 用于控制上游 HTTP 连接池的隔离粒度，影响连接复用和资源消耗

deploy/config.example.yaml

@@ -69,7 +69,7 @@ security:
     # Enable Content-Security-Policy header
     enabled: true
     # Default CSP policy (override if you host assets on other domains)
-    policy: "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' data:; connect-src 'self' https:; frame-ancestors 'none'; base-uri 'self'; form-action 'self'"
+    policy: "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: https:; font-src 'self' data: https://fonts.gstatic.com; connect-src 'self' https:; frame-ancestors 'none'; base-uri 'self'; form-action 'self'"
   proxy_probe:
     # Allow skipping TLS verification for proxy probe (debug only)
     insecure_skip_verify: false