feat: pagination totals, request logging, data retention

Add shared paginate() helper with total count to all list endpoints.
Add request logging middleware (method, path, status, duration, IP).
Add data retention service with configurable thresholds and CLI command.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help build run dev stop logs test migrate clean install start restart status oui
+.PHONY: help build run dev stop logs test migrate clean install start restart status oui cleanup
 
 APP_NAME := esp32-web
 PORT := 5500
@@ -26,6 +26,7 @@ help:
 	@echo "  make install   Install with dev dependencies"
 	@echo "  make test      Run tests"
 	@echo "  make oui       Download OUI database"
+	@echo "  make cleanup   Delete expired data"
 	@echo "  make clean     Remove cache files"
 	@echo ""
 	@echo "Container:"
@@ -85,6 +86,9 @@ test:
 oui:
 	flask --app src/esp32_web download-oui
 
+cleanup:
+	flask --app src/esp32_web cleanup-data
+
 migrate:
 	flask --app src/esp32_web db upgrade