ci(perf): 添加 Lighthouse CI 性能预算回归门槛配置

Phase 2 性能预算重构配套 CI：每次 PR 与每日凌晨 3 点对 /login 路由采样 3 次（desktop preset），断言 LCP <= 3000ms、CLS <= 0.1（error 级），FCP/TBT/INP 为 warn 级。失败时阻断合并并触发性能预算审计报告基线复核。

lighthouserc.json

@@ -0,0 +1,35 @@
+{
+  "ci": {
+    "collect": {
+      "url": [
+        "http://localhost:3000/login"
+      ],
+      "numberOfRuns": 3,
+      "settings": {
+        "preset": "desktop",
+        "throttling": {
+          "rttMs": 40,
+          "throughputKbps": 10240,
+          "cpuSlowdownMultiplier": 1
+        }
+      }
+    },
+    "assert": {
+      "assertions": {
+        "categories:performance": ["warn", { "minScore": 0.85 }],
+        "categories:accessibility": ["error", { "minScore": 0.9 }],
+        "categories:best-practices": ["warn", { "minScore": 0.85 }],
+        "categories:seo": ["warn", { "minScore": 0.85 }],
+        "largest-contentful-paint": ["error", { "maxNumericValue": 3000 }],
+        "cumulative-layout-shift": ["error", { "maxNumericValue": 0.1 }],
+        "interactive": ["warn", { "maxNumericValue": 3000 }],
+        "first-contentful-paint": ["warn", { "maxNumericValue": 2000 }],
+        "total-blocking-time": ["warn", { "maxNumericValue": 300 }]
+      }
+    },
+    "upload": {
+      "target": "filesystem",
+      "outputDir": "lighthouse-results"
+    }
+  }
+}