hotfix(trust-dialog): gate trust UI by signer readiness and harden reputation lookup

In the install trust dialog, stop using profile availability as signed-in signal.
Now we show reputation details and "Always trust" only when both `activePubkey`
and `activeSigner` are available, so the UI matches actual trust persistence capability.

In reputation lookup, make the provider reactive to signer state (`watch` instead
of `read`) and send Vertex DVM params as hex pubkeys (`source` and `target`)
to avoid format issues. Also replace raw reputation errors with the user-facing
message "Service temporarily unavailable."

lib/widgets/relevant_who_follow_container.dart

@@ -192,9 +192,9 @@ class RelevantWhoFollowContainer extends HookConsumerWidget {
             );
           },
         ),
-        AsyncError(:final error) => Center(
+        AsyncError() => Center(
           child: Text(
-            error.toString().replaceFirst('Exception: ', ''),
+            'Service temporarily unavailable.',
             style: baseStyle,
           ),
         ),
@@ -353,16 +353,18 @@ class RelevantWhoFollowContainer extends HookConsumerWidget {
 final relevantWhoFollowProvider = FutureProvider.autoDispose
     .family<List<Profile>, ({String to})>((ref, arg) async {
       // Require active signer and profile to submit the request
-      final signer = ref.read(Signer.activeSignerProvider);
+      final signer = ref.watch(Signer.activeSignerProvider);
       final pubkey = ref.watch(Signer.activePubkeyProvider);
       if (signer == null || pubkey == null) {
         throw 'Not signed in';
       }
 
+      final targetPubkey = arg.to.decodeShareable();
+
       // Build and sign a reputation verification request
       final partial = PartialVerifyReputationRequest(
-        source: pubkey.encodeShareable(type: 'npub'),
-        target: arg.to,
+        source: pubkey,
+        target: targetPubkey,
         limit: 7,
       );
       final request = await partial.signWith(signer);