feat: add SSH key passphrase field and file picker for key path

- Add ssh_key_passphrase field to ConnectionConfig model with full keyring lifecycle
- Pass passphrase to russh load_secret_key for encrypted SSH keys
- Add native file picker (FolderOpen icon) next to SSH key path input
- Add password-type input for key passphrase in connection dialog
- Make connection dialog form scrollable for short windows
- Fix alignment of key path input and browse button
- Add i18n keys (en + zh-CN)

src/i18n/locales/en.ts

@@ -62,6 +62,9 @@ export default {
     sshPassword: "SSH Password",
     sshPasswordPlaceholder: "Leave empty to use key",
     sshKeyPath: "Key Path",
+    sshKeyPassphrase: "Key Passphrase",
+    sshKeyPassphrasePlaceholder: "Leave empty if key is not encrypted",
+    sshKeyPathBrowse: "Browse",
     sshExposeLan: "Expose tunnel to LAN",
     compatible: "Compatible",
     mainstream: "Popular",

src/i18n/locales/zh-CN.ts

@@ -64,6 +64,9 @@ export default {
     sshPassword: "SSH 密码",
     sshPasswordPlaceholder: "留空则使用密钥",
     sshKeyPath: "密钥路径",
+    sshKeyPassphrase: "密钥密码",
+    sshKeyPassphrasePlaceholder: "密钥未加密则留空",
+    sshKeyPathBrowse: "浏览",
     sshExposeLan: "允许局域网访问隧道",
     compatible: "兼容",
     mainstream: "主流",