feat(proxy): HTTP/SOCKS5 代理支持，按会话独立配置 | 15 files +483/-23 | 96/96 tests passing

功能:
- 代理类型定义 (ProxyType, ProxyConfig)
- 代理工具函数 (验证、解析、构建URL) + 24 测试
- SSH 连接通过 HTTP CONNECT / SOCKS5 隧道
- 数据库 proxy 列持久化 (JSON)
- SessionDialog 代理配置 UI (可折叠面板)
- 连接池传递 proxy 到 IPC
- sessionStore 类型添加 proxy 支持

electron/services/database-service.ts

@@ -126,6 +126,13 @@ export class DatabaseService {
       // 列可能已存在，忽略错误
     }
 
+    // 迁移：添加 proxy 列 (JSON 格式存储代理配置)
+    try {
+      this.db.run(`ALTER TABLE sessions ADD COLUMN proxy TEXT`)
+    } catch (e) {
+      // 列可能已存在，忽略错误
+    }
+
     this.db.run(`
       CREATE TABLE IF NOT EXISTS connection_history (
         id TEXT PRIMARY KEY,
@@ -218,8 +225,8 @@ export class DatabaseService {
     logger.info('Creating session:', session.name, session.host)
 
     const stmt = this.prepare(`
-      INSERT INTO sessions (id, name, host, port, username, auth_type, password, private_key_path, passphrase_encrypted, group_name, tags)
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+      INSERT INTO sessions (id, name, host, port, username, auth_type, password, private_key_path, passphrase_encrypted, group_name, tags, proxy)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
     `)
 
     const id = `session-${Date.now()}`
@@ -236,7 +243,8 @@ export class DatabaseService {
       session.privateKey || null,
       this.encryptField(session.passphrase),
       session.group || 'default',
-      session.tags ? JSON.stringify(session.tags) : null
+      session.tags ? JSON.stringify(session.tags) : null,
+      session.proxy ? JSON.stringify(session.proxy) : null
     )
 
     this.save()
@@ -259,6 +267,7 @@ export class DatabaseService {
       password: this.decryptField(s.password as string | null) || undefined,
       privateKey: s.private_key_path as string | undefined,
       passphrase: this.decryptField(s.passphrase_encrypted as string | null) || undefined,
+      proxy: s.proxy ? JSON.parse(s.proxy as string) as Session['proxy'] : undefined,
       group: s.group_name as string | undefined,
       tags: s.tags ? JSON.parse(s.tags as string) as string[] : [],
     }))
@@ -281,6 +290,7 @@ export class DatabaseService {
         password: this.decryptField(session.password as string | null) || undefined,
         privateKey: session.private_key_path as string | undefined,
         passphrase: this.decryptField(session.passphrase_encrypted as string | null) || undefined,
+        proxy: session.proxy ? JSON.parse(session.proxy as string) as Session['proxy'] : undefined,
         group: session.group_name as string | undefined,
         tags: session.tags ? JSON.parse(session.tags as string) as string[] : [],
       }
@@ -334,6 +344,10 @@ export class DatabaseService {
       fields.push('tags = ?')
       values.push(JSON.stringify(updates.tags))
     }
+    if (updates.proxy !== undefined) {
+      fields.push('proxy = ?')
+      values.push(updates.proxy ? JSON.stringify(updates.proxy) : null)
+    }
 
     fields.push('updated_at = CURRENT_TIMESTAMP')
     values.push(id)