fix(安全): 修复依赖漏洞并强化安全扫描

主要改动：
- 固定 Go 1.25.5 与 CI 校验并更新扫描流程
- 升级 quic-go、x/crypto、req 等依赖并通过 govulncheck
- 强化 JWT 校验、TLS 配置与 xlsx 动态加载
- 新增审计豁免清单与校验脚本

.github/workflows/security-scan.yml

@@ -0,0 +1,60 @@
+name: Security Scan
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '0 3 * * 1'
+
+permissions:
+  contents: read
+
+jobs:
+  backend-security:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: backend/go.mod
+          check-latest: false
+          cache-dependency-path: backend/go.sum
+      - name: Verify Go version
+        run: |
+          go version | grep -q 'go1.25.5'
+      - name: Run govulncheck
+        working-directory: backend
+        run: |
+          go install golang.org/x/vuln/cmd/govulncheck@latest
+          govulncheck ./...
+      - name: Run gosec
+        working-directory: backend
+        run: |
+          go install github.com/securego/gosec/v2/cmd/gosec@latest
+          gosec -severity high -confidence high ./...
+
+  frontend-security:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'pnpm'
+          cache-dependency-path: frontend/pnpm-lock.yaml
+      - name: Set up pnpm
+        uses: pnpm/action-setup@v2
+      - name: Install dependencies
+        working-directory: frontend
+        run: pnpm install --frozen-lockfile
+      - name: Run pnpm audit
+        working-directory: frontend
+        run: |
+          pnpm audit --prod --audit-level=high --json > audit.json || true
+      - name: Check audit exceptions
+        run: |
+          python tools/check_pnpm_audit_exceptions.py \
+            --audit frontend/audit.json \
+            --exceptions .github/audit-exceptions.yml