feat(cli): Add deploy list and deploy delete subcommands (#7106)

### Summary
This PR introduces a subcommand implementation that allows `langgraph
deploy list` and `langgraph deploy delete` subcommands.

#### `langgraph deploy list`
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 langgraph % langgraph deploy list --help                                                                              ⎈ gke_langchain-test-387119_us-west1_langgraph-cloud-us-west1
Usage: langgraph deploy list [OPTIONS]

  [Beta] List LangSmith Deployments.

Options:
  --name-contains TEXT  Only show deployments whose names contain this value.
  --api-key TEXT        API key. Can also be set via LANGGRAPH_HOST_API_KEY,
                        LANGSMITH_API_KEY, or LANGCHAIN_API_KEY environment
                        variable or .env file.
  --help                Show this message and exit.
```

Output example:
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy list
Deployment ID                         Deployment Name             Deployment URL                                                                      
------------------------------------  --------------------------  ------------------------------------------------------------------------------------
a40d6567-87c0-485a-a23d-94309a7d4519  ht-andrew-test-04           -                                                                                   
9da26acb-d0c9-4af0-af9e-f3fe8dfe85bc  ht-anirudh-deployment-test  https://ht-anirudh-deployment-test-428af4737f8a533cb2b107587eb8f38f.us.langgraph.app
```

#### `langgraph deploy delete`
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 langgraph % langgraph deploy delete --help                                                                            ⎈ gke_langchain-test-387119_us-west1_langgraph-cloud-us-west1
Usage: langgraph deploy delete [OPTIONS] DEPLOYMENT_ID

  [Beta] Delete a LangSmith Deployment.

Options:
  --force         Delete without prompting for confirmation.
  --api-key TEXT  API key. Can also be set via LANGGRAPH_HOST_API_KEY,
                  LANGSMITH_API_KEY, or LANGCHAIN_API_KEY environment variable
                  or .env file.
  --help          Show this message and exit.
```

Output example:
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy delete a40d6567-87c0-485a-a23d-94309a7d4519
Are you sure you want to delete deployment ID a40d6567-87c0-485a-a23d-94309a7d4519? (Y/n): Y
Host API key: 
Deleted deployment a40d6567-87c0-485a-a23d-94309a7d4519.
```

```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy delete a40d6567-87c0-485a-a23d-94309a7d4519
Are you sure you want to delete deployment ID a40d6567-87c0-485a-a23d-94309a7d4519? (Y/n): n
Aborted!
```

```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy delete 9da26acb-d0c9-4af0-af9e-f3fe8dfe85bc --force
Host API key: 
Deleted deployment 9da26acb-d0c9-4af0-af9e-f3fe8dfe85bc.
```

libs/cli/langgraph_cli/host_backend.py

@@ -39,10 +39,14 @@ class HostBackendClient:
         )
 
     def _request(
-        self, method: str, path: str, payload: dict[str, Any] | None = None
+        self,
+        method: str,
+        path: str,
+        payload: dict[str, Any] | None = None,
+        params: dict[str, Any] | None = None,
     ) -> Any:
         try:
-            resp = self._client.request(method, path, json=payload)
+            resp = self._client.request(method, path, json=payload, params=params)
             resp.raise_for_status()
         except httpx.HTTPStatusError as err:
             detail = err.response.text or str(err.response.status_code)
@@ -65,12 +69,19 @@ class HostBackendClient:
     def create_deployment(self, payload: dict[str, Any]) -> dict[str, Any]:
         return self._request("POST", "/v2/deployments", payload)
 
-    def list_deployments(self, name_contains: str) -> dict[str, Any]:
-        return self._request("GET", f"/v2/deployments?name_contains={name_contains}")
+    def list_deployments(self, name_contains: str = "") -> dict[str, Any]:
+        return self._request(
+            "GET",
+            "/v2/deployments",
+            params={"name_contains": name_contains},
+        )
 
     def get_deployment(self, deployment_id: str) -> dict[str, Any]:
         return self._request("GET", f"/v2/deployments/{deployment_id}")
 
+    def delete_deployment(self, deployment_id: str) -> None:
+        return self._request("DELETE", f"/v2/deployments/{deployment_id}")
+
     def request_push_token(self, deployment_id: str) -> dict[str, Any]:
         return self._request(
             "POST",