Add support for passwordless host authentication

Allow adding SSH hosts without authentication credentials by introducing
a new "none" auth type. This enables users to configure hosts for later
use with SSH agent or manual credential addition.

Changes:
- Add authType "none" to type definitions
- Update frontend form to support "None" authentication option
- Skip credential validation for "none" auth type
- Update backend to accept hosts without credentials
- Add i18n support for English and Chinese

Fixes #278

src/backend/database/routes/ssh.ts

@@ -281,7 +281,14 @@ router.post(
       sshDataObj.keyPassword = keyPassword || null;
       sshDataObj.keyType = keyType;
       sshDataObj.password = null;
+    } else if (effectiveAuthType === "none") {
+      // No authentication credentials - set all to null
+      sshDataObj.password = null;
+      sshDataObj.key = null;
+      sshDataObj.keyPassword = null;
+      sshDataObj.keyType = null;
     } else {
+      // credential type or fallback - set all to null except credentialId
       sshDataObj.password = null;
       sshDataObj.key = null;
       sshDataObj.keyPassword = null;
@@ -471,7 +478,14 @@ router.put(
         sshDataObj.keyType = keyType;
       }
       sshDataObj.password = null;
+    } else if (effectiveAuthType === "none") {
+      // No authentication credentials - set all to null
+      sshDataObj.password = null;
+      sshDataObj.key = null;
+      sshDataObj.keyPassword = null;
+      sshDataObj.keyType = null;
     } else {
+      // credential type or fallback - set all to null except credentialId
       sshDataObj.password = null;
       sshDataObj.key = null;
       sshDataObj.keyPassword = null;
@@ -1356,10 +1370,12 @@ router.post(
           continue;
         }
 
-        if (!["password", "key", "credential"].includes(hostData.authType)) {
+        if (
+          !["password", "key", "credential", "none"].includes(hostData.authType)
+        ) {
           results.failed++;
           results.errors.push(
-            `Host ${i + 1}: Invalid authType. Must be 'password', 'key', or 'credential'`,
+            `Host ${i + 1}: Invalid authType. Must be 'password', 'key', 'credential', or 'none'`,
           );
           continue;
         }
@@ -1391,6 +1407,8 @@ router.post(
           continue;
         }
 
+        // "none" authType requires no validation - no credentials needed
+
         const sshDataObj: any = {
           userId: userId,
           name: hostData.name || `${hostData.username}@${hostData.ip}`,