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

db.go

@@ -3,6 +3,7 @@ package main
 import (
 	"database/sql"
 	"log/slog"
+	"net"
 	"time"
 
 	_ "modernc.org/sqlite"
@@ -180,16 +181,15 @@ func ListTempEntries(db *sql.DB) ([]map[string]interface{}, error) {
 			continue
 		}
 		list = append(list, map[string]interface{}{
-			"ip":       ip,
-			"expires":  expiresAt,
-			"reason":   reason,
+			"ip":      ip,
+			"expires": expiresAt,
+			"reason":  reason,
 		})
 	}
 	return list, nil
 }
 
 func ipMatchesEntry(ip, entry string) (bool, error) {
-	// Simple case: exact IP match
 	if entry == ip {
 		return true, nil
 	}
@@ -222,4 +222,4 @@ func isUniqueConstraintError(err error) bool {
 		return false
 	}
 	return err.Error() == "UNIQUE constraint failed: permanent_whitelist.entry"
-}
+}