fix: dedupe and report automatic template creation from images

install_appliances_from_image relied on the name+version pair check in
TemplatesService, so the same appliance reached through a second image
(the CSR1000v case) created a second template sharing the name. The auto
path now skips when any template with the same name exists, whatever the
version, and returns a manifest of created and skipped candidates;
POST /images/install replies 200 with that manifest instead of an empty
204, and the image_install MCP tool surfaces it.

tests/agent/mcp/test_handlers.py

@@ -523,6 +523,36 @@ class TestTemplate:
             assert "deleted" in str(result).lower()
 
 
+# ── Image ───────────────────────────────────────────────────────────────
+
+
+class TestImage:
+
+    mod = "images"
+
+    def test_install_manifest(self, ctx):
+        from gns3server.agent.mcp.images import install_images_handler
+        with patch(f"{BASE}.{self.mod}._get_connector") as m:
+            conn = _mock_conn({
+                "created": [{"template_id": "t1", "name": "Empty VM", "version": "100G", "template_type": "qemu"}],
+                "skipped": [{"name": "csr1000v.qcow2", "reason": "image is already used by one or more templates"}],
+            })
+            m.return_value = conn
+            result = install_images_handler({}, ctx)
+            assert result["created"][0]["name"] == "Empty VM"
+            assert result["skipped"][0]["name"] == "csr1000v.qcow2"
+
+    def test_install_empty_body(self, ctx):
+        from gns3server.agent.mcp.images import install_images_handler
+        with patch(f"{BASE}.{self.mod}._get_connector") as m:
+            conn = _mock_conn()
+            conn.http_call.return_value.content = b""
+            conn.http_call.return_value.json.side_effect = json.JSONDecodeError("Expecting value", "", 0)
+            m.return_value = conn
+            result = install_images_handler({}, ctx)
+            assert result == {"message": "Image installation completed"}
+
+
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