feat: add GET /api/peers/<peer_name> endpoint

Allows fetching a single peer by name. E2E tests need this to verify
persisted peer state after PUT operations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/routes/peers.py

@@ -183,6 +183,19 @@ def add_peer():
         return jsonify({"error": str(e)}), 500
 
 
+@bp.route('/api/peers/<peer_name>', methods=['GET'])
+def get_peer(peer_name):
+    try:
+        from app import peer_registry
+        peer = peer_registry.get_peer(peer_name)
+        if peer is None:
+            return jsonify({'error': 'Peer not found'}), 404
+        return jsonify(peer)
+    except Exception as e:
+        logger.error(f"Error getting peer {peer_name}: {e}")
+        return jsonify({"error": str(e)}), 500
+
+
 @bp.route('/api/peers/<peer_name>', methods=['PUT'])
 def update_peer(peer_name):
     try: