Expose object type templates via API / MCP

Problem: getObjectTypeShape returns the writable property schema for an object type, but not any of the templates configured for that type in the UI. Capacities allows multiple templates per object type, each with preset field values, tags, and body/content structure — none of this is exposed via API.

Request: Add an endpoint that, for a given object type, returns all templates configured for it: template name/ID, preset property values, preset tags, and default body/content structure. Ideally also allow specifying a template ID at object-creation time so createObjectViaMD can pre-fill from it. Should work generically for any object type with templates, not restricted to built-in types.

Why it matters: without this, objects created via API/MCP have no access to any template structure the user built in the UI — every API-created object starts blank relative to what "New [Type]" in the app would produce, with no way to enumerate or select templates programmatically.