Implement SSH port forwarding and improve jump host UI

Port Forwarding (new):
- Add PortForward model with local/remote direction, bind/dest addresses
- Implement ForwardManager in sshclient/portforward.go with full
  bidirectional tunnel support for both local and remote forwarding
- Integrate ForwardManager into SSH client lifecycle (auto-start on
  connect, clean shutdown on close)
- Add session manager methods: ListPortForwards, StartPortForward,
  StopPortForward with event emission
- Add API surface: ListPortForwards, StartPortForward, StopPortForward
- Add validation for port-forward rules in ValidateSSHConfig
- Add port forwarding section to profile editor with direction, bind/dest
  host/port, label, and enable toggle
- Add frontend event handling for forward:started/stopped/error
- Style port-forward rows with charcoal card design matching jump hosts

Jump Host UI improvements:
- Add private key path field to jump host editor rows
- Collect privateKeyPath in form value collection
- Restyle jump host rows as two-line cards with clear field grouping

frontend/wailsjs/go/api/Service.js

@@ -90,6 +90,10 @@ export function ListKnownHosts() {
   return window['go']['api']['Service']['ListKnownHosts']();
 }
 
+export function ListPortForwards(arg1) {
+  return window['go']['api']['Service']['ListPortForwards'](arg1);
+}
+
 export function ListProfiles() {
   return window['go']['api']['Service']['ListProfiles']();
 }
@@ -178,6 +182,14 @@ export function SetProfileSecret(arg1, arg2, arg3) {
   return window['go']['api']['Service']['SetProfileSecret'](arg1, arg2, arg3);
 }
 
+export function StartPortForward(arg1, arg2) {
+  return window['go']['api']['Service']['StartPortForward'](arg1, arg2);
+}
+
+export function StopPortForward(arg1, arg2) {
+  return window['go']['api']['Service']['StopPortForward'](arg1, arg2);
+}
+
 export function TestConnection(arg1, arg2) {
   return window['go']['api']['Service']['TestConnection'](arg1, arg2);
 }