[Subtask] feat(mcp-server): write tools for views (create/alter/drop)

### Describe the subtask

Follow-up to #12129, which added the read-only view tools and noted that
create/alter/drop could be a later subtask. This is that subtask.

View is currently the only peer entity in the MCP server with no write tools:
catalog, schema, table and fileset have create/alter/drop, topic/model/tag have
their equivalents, while view has only `list_of_views` and `load_view`.

Proposed tools, following the established pattern (interface → plain REST client
→ FastMCP tool → mock → unit tests):

- `create_view` — `POST .../schemas/{schema}/views`
- `alter_view` — `PUT .../schemas/{schema}/views/{view}`
- `drop_view` — `DELETE .../schemas/{schema}/views/{view}`

The backend REST already exists (`ViewOperations`), so this is a client-side
addition only.

I'll submit a PR shortly. cc @yuqi1129

### Parent issue

#11573