Add template `build-v2` command that uses template SDK
<!-- CURSOR_SUMMARY -->
---
> [!NOTE]
> Introduce `template build-v2` command that builds templates directly
from a Dockerfile via the Template SDK and wire it into the CLI.
>
> - **CLI - Template**:
> - **New Command**: `template build-v2`
(`packages/cli/src/commands/template/build-v2.ts`)
> - Builds from Dockerfile using SDK:
`Template(...).fromDockerfile(...)` and `Template.build(...)`.
> - Options: `--dockerfile`, `--cmd`, `--ready-cmd`, `--cpu-count`,
`--memory-mb`, `--no-cache`, path via `--path`; alias `bd-v2`.
> - Validations: template name format, even `memory-mb`.
> - Auth/config: uses access token, API key, domain; streams build logs;
prints success examples.
> - **Wiring**: Add `buildV2Command` to
`packages/cli/src/commands/template/index.ts`.
> - **Release**: Changeset adds patch for `@e2b/cli`.
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
33578b56dfbcd76c3bb2ecf7fdf6f2cb80c3d0dd. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
Jakub Dobry
a0b6104320