Introduce SFTP Web Publishing Support for iOS

This PR ports the macOS SFTP web publishing feature to iOS, enabling users to publish and manage notes on a custom server directly from the iOS app.

What's Changed

SFTPUploader

• New class built on top of Shout for SSH/SFTP connectivity
• Supports uploading and removing notes from a remote server
• Key-based authentication via temporary key files (written to the app's temp directory and cleaned up after use)
• Descriptive error wrapping for actionable failure messages

SFTPViewController

• New settings screen for configuring the SFTP connection
• Fields: host, port, remote path, web URL, username, password, passphrase
• Import and delete private/public key files
• Test Connection button to validate credentials before use
• Toggle to enable/disable the custom SFTP server

Persistence & Integration

• Public key data persisted via UserDefaultsManagement
• SFTP settings wired into SettingsViewController
• NotesTableView Create/Update/Delete web actions now invoke SFTPUploader when the custom server toggle is enabled

Localization

• Added localization keys and placeholder strings for all new UI elements

Project

• Updated project.pbxproj to include new source files
• Added required entitlements and project settings for outgoing network connections

Testing

• Test connection with password auth
• Test connection with key-based auth (RSA / Ed25519)
• Upload a note and verify it appears at the configured web URL
• Delete a note and verify removal from the server
• Verify keys are not persisted to disk after session ends
• Verify graceful error messages on bad credentials / unreachable host
• Test on both iPhone and iPad
• Localization strings

Notes

• Still figuring out why is required to select both: Private Key and Public Key(in original macOS implementation)
• Private keys are written to a temporary file only for the duration of the SFTP session and are deleted immediately after
• The SFTP toggle in settings mirrors the existing macOS behaviour — when disabled, the app falls back to the default sharing path
• If required, I can provide a test SFTP server.

Result