Add lifecycle overview documentation page

Summary

Add a documentation page that explains the AgentSeek project lifecycle from creation to operation.

Requirements

• Add a lifecycle overview page under the docs tree.
• Cover the main flow: create, configure, run, extend, build, deploy, and operate.
• Link each stage to the existing tutorial, how-to, reference, or concept page that owns the detailed steps.
• Keep the page conceptual and navigational; do not duplicate full command references.
• Add the page to the MkDocs navigation.

Acceptance Criteria

• The page gives readers a single lifecycle map for AgentSeek projects.
• Links point to existing docs pages and resolve in the MkDocs build.
• uv run mkdocs build -s passes.