Add signatory-only sign button to Bridge screen

Any of the USDT bridge multisig's 5 known signatories now sees a
status button on the Bridge screen: green when the automation key's
spending allowance is healthy, red with a Sign action once it drops
below threshold. Signing submits the renewal's as_multi approval
directly from the wallet, mirroring the same on-chain action already
available via pwap-web and pezbridge-sign.pex.mom - a third
independent channel for the same operation, none of which is a
single point of failure.

feature-assets/src/main/res/layout/fragment_bridge.xml

@@ -330,6 +330,17 @@
                 android:textSize="12sp"
                 android:visibility="gone" />
 
+            <!-- Multisig signatory-only bridge allowance sign button. Only visible to a wallet
+                 that is one of the bridge multisig's 5 known signatories. -->
+            <io.novafoundation.nova.common.view.PrimaryButton
+                android:id="@+id/bridgeSignButton"
+                style="@style/Widget.Nova.Button.Primary"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="16dp"
+                android:text="@string/bridge_sign_button"
+                android:visibility="gone" />
+
         </LinearLayout>
 
     </ScrollView>