fix(fx): commit proxy port field on focus loss, not only on Enter

[mjakubicek]

The Proxy Port field in TSA/Validation settings only wrote the typed value back to the view model via setOnAction(), which JavaFX only fires on Enter in that field. Typing a port and then clicking elsewhere (Save, another field, another tab) leaves the on-screen text unpersisted, so buildProxyConfig() (DssSigningEngine) silently uses whatever was last committed - Constants.DEFVAL_PROXY_PORT (80) if nothing ever was - while the proxy host (bound bidirectionally) updates correctly. This produces a confusing failure: DSS connects to the configured proxy host on port 80 instead of the port shown in the settings dialog.

txtProxyHost already uses a proper bindBidirectional(); the port needs manual String<->int handling, but was missing the focus-loss commit that the same pattern already uses elsewhere in this codebase (see commitFontSize() / txtFontSize in SignatureSettingsController), which commits on both Enter and focus-loss and reverts to the last valid value on parse failure. This mirrors that same pattern for consistency.

[kwart]

Merged, thanks! Good catch.

Two paths the focus-loss listener can't reach, so I followed up in #513: menu accelerators (Shortcut+S/Shortcut+T) fire without moving the scene focus owner, and WINDOW_CLOSE_REQUEST runs before the stage hides — so signing via Ctrl+S or closing the window still used the last committed port. #513 commits both numeric fields explicitly before every syncToOptions(), and adds range checks plus tests.