feat(admin): add ephemeral staging DB, read-only posts overview, and dynamic search

- Implement ephemeral staging mode (APP_ENV=staging) to isolate test/dev DB writes in /tmp
- Add read-only posts management dashboard under /guanli/posts with live links and comment counters
- Add hot re-indexing endpoint (/guanli/reindex) to refresh Markdown without restarting server
- Replace static recommended search config with dynamic frequency-based trending searches
- Remove early scaffold mockup file (dropbox/zh.md) and clean legacy mock test queries
- Add native Makefile with dev, dev-persistent, test, lint, and docker targets
- Update test suite and documentation for development workflows

package.json

@@ -5,9 +5,10 @@
   "main": "server/index.js",
   "scripts": {
     "start": "node server/index.js",
-    "dev": "node --watch --watch-path=server --watch-path=views --watch-path=public server/index.js",
+    "dev": "APP_ENV=staging node --watch --watch-path=server --watch-path=views --watch-path=public server/index.js",
+    "dev:persistent": "node --watch --watch-path=server --watch-path=views --watch-path=public server/index.js",
     "lint": "node scripts/lint.js",
-    "test": "node test/test.js"
+    "test": "NODE_ENV=test node test/test.js"
   },
   "keywords": ["blog", "k8s", "ssr", "express", "markdown"],
   "author": "Pengzhan Hao",