feat: add SQLite persistence and REST API for temporary whitelisting

- Migrate IP-based temporary whitelisting from file to SQLite storage
- Add REST API endpoints for managing temporary and permanent whitelists
- Create `.env.example` with required environment variables
- Document API endpoints in README.md and docs/api.md
- Add new dependency `modernc.org/sqlite` for SQLite support
- Update deployment and security documentation

go.mod

@@ -1,3 +1,17 @@
 module go.mod
 
 go 1.25.0
+
+require modernc.org/sqlite v1.50.0
+
+require (
+	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/ncruces/go-strftime v1.0.0 // indirect
+	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	golang.org/x/sys v0.42.0 // indirect
+	modernc.org/libc v1.72.0 // indirect
+	modernc.org/mathutil v1.7.1 // indirect
+	modernc.org/memory v1.11.0 // indirect
+)