Align CLI documentation with its PostgreSQL runtime dependency

[javiertoledo]

Context

Raised while reviewing #43. README.md calls the operator CLI “zero-dependency”, but the published package declares postgres. facility instance bootstrap imports and opens that client, and the authentication guide explicitly documents its direct PostgreSQL connection.

Problem

The package-level “zero-dependency” claim no longer matches the deliberate PostgreSQL-backed instance bootstrap added in e92c706. It misstates the published artifact's runtime contract and can send future reviews toward removing behavior the self-host bootstrap requires.

Proposed change

Replace the blanket claim with wording that accurately describes the CLI, and audit the public CLI/package documentation for the same promise. Keep the direct PostgreSQL bootstrap behavior and its runtime dependency explicit.

Why not in #43

#43 adds release plumbing and relocates existing README sections; it did not introduce the PostgreSQL bootstrap design. Resolving the product/documentation contract belongs in a focused follow-up.

Acceptance criteria

• Public documentation no longer describes the whole CLI as zero-dependency while postgres ships in its runtime dependencies.
• facility instance bootstrap remains documented as connecting directly to PostgreSQL.
• Package metadata and CLI documentation describe the same runtime requirements.