Add optional password requirement for SSH sessions (Issue #118)

Users can now choose whether to require a password when saving SSH sessions.
A new "Require Password" toggle has been added to the password authentication
tab, allowing sessions to be saved without entering a password when disabled.

- Add requirePassword boolean field to SSH host schema (defaults to true)
- Update form validation to conditionally require password based on setting
- Add "Require Password" toggle with description in Host Manager UI
- Update all backend SSH routes to handle requirePassword field correctly
- Add translations for new UI elements in English and Chinese
- Maintain full backward compatibility with existing hosts

Resolves #118

src/backend/database/db/schema.ts

@@ -45,6 +45,9 @@ export const sshData = sqliteTable("ssh_data", {
   authType: text("auth_type").notNull(),
 
   password: text("password"),
+  requirePassword: integer("require_password", { mode: "boolean" })
+    .notNull()
+    .default(true),
   key: text("key", { length: 8192 }),
   keyPassword: text("key_password"),
   keyType: text("key_type"),