feat: implement comprehensive SSH credentials management system

- Add complete SSH credentials CRUD operations with AES-256 encryption
- Implement database migration system for schema versioning
- Create modern UI with Zinc theme for credentials management
- Add credential viewer and editor with responsive design
- Support password and SSH key authentication methods
- Include usage tracking and folder organization
- Enhance sidebar width and improve page spacing
- Add comprehensive i18n support (EN/ZH)
- Integrate with existing SSH host management

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

public/locales/en/translation.json

@@ -1,4 +1,103 @@
 {
+  "credentials": {
+    "credentialsManager": "Credentials Manager",
+    "manageYourSSHCredentials": "Manage your SSH credentials securely",
+    "addCredential": "Add Credential",
+    "createCredential": "Create Credential",
+    "editCredential": "Edit Credential",
+    "viewCredential": "View Credential",
+    "duplicateCredential": "Duplicate Credential",
+    "deleteCredential": "Delete Credential",
+    "updateCredential": "Update Credential",
+    "credentialName": "Credential Name",
+    "credentialDescription": "Description",
+    "searchCredentials": "Search credentials...",
+    "selectFolder": "Select Folder",
+    "selectAuthType": "Select Auth Type",
+    "allFolders": "All Folders",
+    "allAuthTypes": "All Auth Types",
+    "uncategorized": "Uncategorized",
+    "totalCredentials": "Total",
+    "keyBased": "Key-based",
+    "passwordBased": "Password-based",
+    "folders": "Folders",
+    "noCredentialsMatchFilters": "No credentials match your filters",
+    "noCredentialsYet": "No credentials created yet",
+    "createFirstCredential": "Create your first credential",
+    "failedToFetchCredentials": "Failed to fetch credentials",
+    "credentialDeletedSuccessfully": "Credential deleted successfully",
+    "failedToDeleteCredential": "Failed to delete credential",
+    "confirmDeleteCredential": "Are you sure you want to delete credential \"{{name}}\"?",
+    "credentialCreatedSuccessfully": "Credential created successfully",
+    "credentialUpdatedSuccessfully": "Credential updated successfully",
+    "failedToSaveCredential": "Failed to save credential",
+    "failedToFetchCredentialDetails": "Failed to fetch credential details",
+    "failedToFetchHostsUsing": "Failed to fetch hosts using this credential",
+    "basicInfo": "Basic Info",
+    "authentication": "Authentication",
+    "organization": "Organization",
+    "basicInformation": "Basic Information",
+    "basicInformationDescription": "Enter the basic information for this credential",
+    "authenticationMethod": "Authentication Method",
+    "authenticationMethodDescription": "Choose how you want to authenticate with SSH servers",
+    "organizationDescription": "Organize your credentials with folders and tags",
+    "enterCredentialName": "Enter credential name",
+    "enterCredentialDescription": "Enter description (optional)",
+    "enterUsername": "Enter username",
+    "nameIsRequired": "Credential name is required",
+    "usernameIsRequired": "Username is required",
+    "authenticationType": "Authentication Type",
+    "passwordAuthDescription": "Use password authentication",
+    "sshKeyAuthDescription": "Use SSH key authentication",
+    "passwordIsRequired": "Password is required",
+    "sshKeyIsRequired": "SSH key is required",
+    "sshKeyType": "SSH Key Type",
+    "privateKey": "Private Key",
+    "enterPassword": "Enter password",
+    "enterPrivateKey": "Enter private key",
+    "keyPassphrase": "Key Passphrase",
+    "enterKeyPassphrase": "Enter key passphrase (optional)",
+    "keyPassphraseOptional": "Optional: leave empty if your key has no passphrase",
+    "leaveEmptyToKeepCurrent": "Leave empty to keep current value",
+    "uploadKeyFile": "Upload Key File",
+    "generateKeyPair": "Generate Key Pair",
+    "sshKeyGenerationNotImplemented": "SSH key generation feature coming soon",
+    "connectionTestingNotImplemented": "Connection testing feature coming soon",
+    "testConnection": "Test Connection",
+    "selectOrCreateFolder": "Select or create folder",
+    "noFolder": "No folder",
+    "orCreateNewFolder": "Or create new folder",
+    "addTag": "Add tag",
+    "saving": "Saving...",
+    "overview": "Overview",
+    "security": "Security",
+    "usage": "Usage",
+    "securityDetails": "Security Details",
+    "securityDetailsDescription": "View encrypted credential information",
+    "credentialSecured": "Credential Secured",
+    "credentialSecuredDescription": "All sensitive data is encrypted with AES-256",
+    "passwordAuthentication": "Password Authentication",
+    "keyAuthentication": "Key Authentication",
+    "keyType": "Key Type",
+    "securityReminder": "Security Reminder",
+    "securityReminderText": "Never share your credentials. All data is encrypted at rest.",
+    "hostsUsingCredential": "Hosts Using This Credential",
+    "noHostsUsingCredential": "No hosts are currently using this credential",
+    "timesUsed": "Times Used",
+    "lastUsed": "Last Used",
+    "connectedHosts": "Connected Hosts",
+    "created": "Created",
+    "lastModified": "Last Modified",
+    "usageStatistics": "Usage Statistics",
+    "copiedToClipboard": "{{field}} copied to clipboard",
+    "failedToCopy": "Failed to copy to clipboard",
+    "sshKey": "SSH Key",
+    "createCredentialDescription": "Create a new SSH credential for secure access",
+    "editCredentialDescription": "Update the credential information",
+    "listView": "List",
+    "folderView": "Folders",
+    "unknown": "Unknown"
+  },
   "sshTools": {
     "title": "SSH Tools",
     "closeTools": "Close SSH Tools",
@@ -120,6 +219,7 @@
   "nav": {
     "home": "Home",
     "hosts": "Hosts",
+    "credentials": "Credentials",
     "terminal": "Terminal",
     "tunnels": "Tunnels",
     "fileManager": "File Manager",