feat(stockbit): print the ssh forward when the shell is remote

The login page listens on 127.0.0.1, so a browser on the Mac driving a VM
could never reach it. Over SSH, idx now picks port 7878, skips opening a
browser on the VM, and prints the exact ssh -L to run where the browser
is.

crates/idx-core/src/api/stockbit/loopback.rs

@@ -62,6 +62,11 @@ impl LoginPage {
         format!("http://127.0.0.1:{}/login/{}", self.port, self.secret)
     }
 
+    /// The port the page listens on.
+    pub fn port(&self) -> u16 {
+        self.port
+    }
+
     /// Serves until `verify` accepts a paste or `timeout` passes. `verify`
     /// returns the error text to show on the page when the paste is refused.
     ///