feat: 新增 IPv6 双栈支持

- 协议: InitMessage 增加 ip6/prefix6/server_ip6 字段(omitempty,向后兼容)
- TUN: Device 接口新增 ConfigureIPv6, macOS 用 ifconfig inet6, Linux 用 ip -6 addr add
- 路由: full 模式自动添加 ::/1+8000::/1, v6 服务器旁路 /128, resolveHosts 双栈解析
- 会话: setupTUN 解析 v6 字段并配置 TUN+路由, connectOnce 传 v6 给 stats/日志
- 统计: SetConnected(ip,ip6), Snapshot.AssignedIP6
- DB: connection_logs 增加 assigned_ip6 列 + migrateV3 幂等迁移
- UI: 状态卡片新增独立 IPv6 行, 始终可见(未获取显示 IPv6: —)
- 文档: 同步 client-development.md 至服务端 IPv6 版本

internal/db/db.go

@@ -45,7 +45,10 @@ func (s *Store) migrate() error {
 	if err != nil {
 		return err
 	}
-	return s.migrateV2()
+	if err := s.migrateV2(); err != nil {
+		return err
+	}
+	return s.migrateV3()
 }
 
 func (s *Store) migrateV2() error {
@@ -165,6 +168,41 @@ func nullStr(s sql.NullString) sql.NullString {
 	return s
 }
 
+// migrateV3 adds the assigned_ip6 column to connection_logs for IPv6
+// dual-stack support. Idempotent: skips if the column already exists.
+func (s *Store) migrateV3() error {
+	if columnExists(s.db, "connection_logs", "assigned_ip6") {
+		return nil
+	}
+	_, err := s.db.Exec(`ALTER TABLE connection_logs ADD COLUMN assigned_ip6 TEXT NOT NULL DEFAULT ''`)
+	if err != nil {
+		return fmt.Errorf("migrate v3 add assigned_ip6: %w", err)
+	}
+	return nil
+}
+
+// columnExists reports whether a column exists on a table.
+func columnExists(db *sql.DB, table, column string) bool {
+	rows, err := db.Query(fmt.Sprintf("PRAGMA table_info(%s)", table))
+	if err != nil {
+		return false
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var cid int
+		var name, ctype string
+		var notnull, pk int
+		var dflt sql.NullString
+		if err := rows.Scan(&cid, &name, &ctype, &notnull, &dflt, &pk); err != nil {
+			return false
+		}
+		if name == column {
+			return true
+		}
+	}
+	return false
+}
+
 const schemaV2 = `
 CREATE TABLE IF NOT EXISTS server_profiles (
 	id              INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -185,15 +223,16 @@ CREATE TABLE IF NOT EXISTS server_profiles (
 );
 
 CREATE TABLE IF NOT EXISTS connection_logs (
-	id          INTEGER PRIMARY KEY AUTOINCREMENT,
-	profile_id  INTEGER NOT NULL,
-	started_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
-	ended_at    DATETIME,
-	assigned_ip TEXT    NOT NULL DEFAULT '',
-	rx_bytes    INTEGER NOT NULL DEFAULT 0,
-	tx_bytes    INTEGER NOT NULL DEFAULT 0,
-	status      TEXT    NOT NULL DEFAULT 'connected',
-	error_msg   TEXT    NOT NULL DEFAULT '',
+	id           INTEGER PRIMARY KEY AUTOINCREMENT,
+	profile_id   INTEGER NOT NULL,
+	started_at   DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+	ended_at     DATETIME,
+	assigned_ip  TEXT    NOT NULL DEFAULT '',
+	assigned_ip6 TEXT    NOT NULL DEFAULT '',
+	rx_bytes     INTEGER NOT NULL DEFAULT 0,
+	tx_bytes     INTEGER NOT NULL DEFAULT 0,
+	status       TEXT    NOT NULL DEFAULT 'connected',
+	error_msg    TEXT    NOT NULL DEFAULT '',
 	FOREIGN KEY (profile_id) REFERENCES server_profiles(id) ON DELETE CASCADE
 );
 

internal/db/log.go

@@ -21,13 +21,13 @@ func (s *Store) StartLog(profileID int64) (int64, error) {
 }
 
 // FinishLog finalises a connection log entry with final stats.
-func (s *Store) FinishLog(id int64, status model.ConnectionStatus, assignedIP string, rxBytes, txBytes int64, errMsg string) error {
+func (s *Store) FinishLog(id int64, status model.ConnectionStatus, assignedIP, assignedIP6 string, rxBytes, txBytes int64, errMsg string) error {
 	_, err := s.db.Exec(
 		`UPDATE connection_logs SET
-		    ended_at = ?, assigned_ip = ?, rx_bytes = ?, tx_bytes = ?,
+		    ended_at = ?, assigned_ip = ?, assigned_ip6 = ?, rx_bytes = ?, tx_bytes = ?,
 		    status = ?, error_msg = ?
 		 WHERE id = ?`,
-		time.Now(), assignedIP, rxBytes, txBytes, status, errMsg, id)
+		time.Now(), assignedIP, assignedIP6, rxBytes, txBytes, status, errMsg, id)
 	if err != nil {
 		return fmt.Errorf("finish log %d: %w", id, err)
 	}
@@ -37,7 +37,7 @@ func (s *Store) FinishLog(id int64, status model.ConnectionStatus, assignedIP st
 // RecentLogs returns the most recent N connection logs for a profile.
 func (s *Store) RecentLogs(profileID int64, limit int) ([]model.ConnectionLog, error) {
 	rows, err := s.db.Query(
-		`SELECT id, profile_id, started_at, ended_at, assigned_ip,
+		`SELECT id, profile_id, started_at, ended_at, assigned_ip, assigned_ip6,
 		        rx_bytes, tx_bytes, status, error_msg
 		 FROM connection_logs WHERE profile_id = ?
 		 ORDER BY started_at DESC LIMIT ?`,
@@ -52,7 +52,7 @@ func (s *Store) RecentLogs(profileID int64, limit int) ([]model.ConnectionLog, e
 		var l model.ConnectionLog
 		var ended interface{}
 		if err := rows.Scan(&l.ID, &l.ProfileID, &l.StartedAt, &ended,
-			&l.AssignedIP, &l.RxBytes, &l.TxBytes, &l.Status, &l.ErrorMsg); err != nil {
+			&l.AssignedIP, &l.AssignedIP6, &l.RxBytes, &l.TxBytes, &l.Status, &l.ErrorMsg); err != nil {
 			return nil, err
 		}
 		if t, ok := ended.(time.Time); ok {