chore: bootstrap housing research platform

config/source_catalog.json

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+{
+  "official_sources": [
+    {
+      "name": "上海市统计局",
+      "url": "https://tjj.sh.gov.cn/",
+      "cadence": "monthly",
+      "use": "房地产开发投资、商品房销售、宏观人口与收入数据",
+      "reliability": "high"
+    },
+    {
+      "name": "上海市房屋管理局",
+      "url": "https://fgj.sh.gov.cn/",
+      "cadence": "event/monthly",
+      "use": "房产交易、政策通知、市场监管信息",
+      "reliability": "high"
+    },
+    {
+      "name": "上海土地市场",
+      "url": "https://biz.ghzyj.sh.gov.cn/shtdsc/wz/tdjy/index.jhtml",
+      "cadence": "event",
+      "use": "住宅用地公告、成交、楼面价、溢价率",
+      "reliability": "high"
+    },
+    {
+      "name": "中国货币网 LPR",
+      "url": "https://www.chinamoney.com.cn/chinese/bklpr/",
+      "cadence": "monthly",
+      "use": "贷款市场报价利率，尤其是五年期以上 LPR",
+      "reliability": "high"
+    }
+  ],
+  "market_sources": [
+    {
+      "name": "中介挂牌与成交数据",
+      "url": null,
+      "cadence": "daily/weekly",
+      "use": "挂牌量、挂牌价、成交周期、议价空间、小区微观样本",
+      "reliability": "medium",
+      "note": "需要记录采集时间、口径、去重规则和合规边界。"
+    },
+    {
+      "name": "租赁平台样本",
+      "url": null,
+      "cadence": "weekly/monthly",
+      "use": "租金、空置压力、租售比、板块居住需求",
+      "reliability": "medium",
+      "note": "挂牌租金不等于成交租金，应单独标注。"
+    }
+  ]
+}