Scaffold the standalone Rust Apollo CLI

## Background Refs #5624. This is the first implementation task for Apollo CLI v0. It should create the standalone Rust CLI foundation that later auth/profile, OpenAPI, and command UX work can build on. ## Goal Scaffold a standalone Rust CLI named `apollo` with the minimum project structure, command framework, test setup, and CI/release foundations needed for later phases. ## Proposed scope - Create a standalone Rust CLI project for the `apollo` executable. - Choose and document the command-line framework, for example `clap` or an equivalent Rust CLI framework. - Add top-level command routing for the planned v0 groups: - `auth` - `profile` - `app` - `env` - `namespace` - `config` - `release` - `api` - Add global flags that can be wired later: - `--profile` - `--server` - `--output json|table` - `--yes` - Add a basic output abstraction so commands do not print ad hoc strings directly. - Add a basic error abstraction so structured errors can be added consistently. - Add unit test and integration test scaffolding. - Add developer documentation for local build/test commands. ## Out of scope - Calling Apollo OpenAPI endpoints. - Implementing token storage. - Implementing full command behavior beyond skeleton commands. - Implementing agent session authorization, MCP, or any Apollo server-side changes. ## Acceptance criteria - `apollo --help` works and shows the planned v0 command groups. - Global flags are parsed consistently. - Placeholder command handlers return structured placeholder errors rather than panics. - The project has documented build and test commands. - CI can run formatting, linting, and tests for the Rust CLI. - No deprecated Portal WebAPI path is introduced.