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

Makefile

@@ -0,0 +1,52 @@
+.PHONY: help dev dev-persistent test lint clean docker-build docker-run
+
+# Default target
+all: help
+
+help:
+	@echo "========================================================================"
+	@echo " pengzhan.dev — Engineering Makefile"
+	@echo "========================================================================"
+	@echo "Available commands:"
+	@echo "  make dev             Start local server in Ephemeral Staging Mode"
+	@echo "                       (Safe by default: site.db is NEVER mutated)"
+	@echo "  make dev-persistent  Start local server in Persistent DB Mode"
+	@echo "                       (Changes to comments & logs write to site.db)"
+	@echo "  make test            Run complete automated test suite (in isolated temp DB)"
+	@echo "  make lint            Run comprehensive project linter (JS, EJS, CSS)"
+	@echo "  make clean           Remove temporary staging DBs and build caches"
+	@echo "  make docker-build    Build multi-stage production Docker image"
+	@echo "  make docker-run      Run production Docker container on port 3000"
+	@echo "========================================================================"
+
+dev:
+	@echo "Starting dev server in Safe Ephemeral Staging Mode..."
+	@echo "-> Production sample-content/data/site.db is protected from writes."
+	APP_ENV=staging node --watch --watch-path=server --watch-path=views --watch-path=public server/index.js
+
+dev-persistent:
+	@echo "Starting dev server in Persistent DB Mode..."
+	@echo "-> Writes will be recorded to sample-content/data/site.db."
+	node --watch --watch-path=server --watch-path=views --watch-path=public server/index.js
+
+test:
+	@echo "Running automated test suite..."
+	NODE_ENV=test node test/test.js
+
+lint:
+	@echo "Running project linter..."
+	node scripts/lint.js
+
+clean:
+	@echo "Cleaning temporary test and staging artifacts..."
+	@rm -f /tmp/site.staging-*.db /tmp/site.staging-*.db-*
+	@rm -f sample-content/data/*.db-journal sample-content/data/*.db-wal sample-content/data/*.db-shm
+	@echo "Clean complete."
+
+docker-build:
+	@echo "Building Docker image pengzhan.dev:latest..."
+	docker build -t pengzhan.dev:latest .
+
+docker-run:
+	@echo "Running Docker container on http://localhost:3000..."
+	docker run --rm -p 3000:3000 -v $(PWD)/sample-content:/app/content pengzhan.dev:latest