Fix prefix stats by counting from live routes tables

The prefixes_v4 and prefixes_v6 tables were never being populated
because GetOrCreatePrefix was not being called anywhere. Since we
already track all prefixes in live_routes_v4 and live_routes_v6,
update stats queries to count distinct prefixes from those tables.

internal/database/database.go

@@ -815,13 +815,13 @@ func (d *Database) GetStatsContext(ctx context.Context) (Stats, error) {
 		return stats, err
 	}
 
-	// Count prefixes from both tables
-	err = d.db.QueryRowContext(ctx, "SELECT COUNT(*) FROM prefixes_v4").Scan(&stats.IPv4Prefixes)
+	// Count unique prefixes from live routes tables
+	err = d.db.QueryRowContext(ctx, "SELECT COUNT(DISTINCT prefix) FROM live_routes_v4").Scan(&stats.IPv4Prefixes)
 	if err != nil {
 		return stats, err
 	}
 
-	err = d.db.QueryRowContext(ctx, "SELECT COUNT(*) FROM prefixes_v6").Scan(&stats.IPv6Prefixes)
+	err = d.db.QueryRowContext(ctx, "SELECT COUNT(DISTINCT prefix) FROM live_routes_v6").Scan(&stats.IPv6Prefixes)
 	if err != nil {
 		return stats, err
 	}