feat: anonymous / blind-review mode

[smur89]

Problem

Some hiring processes use blind reviews — interviewers see candidate skills and experience without name, photo, or contact details. There's no easy way to redact the header today; users have to fork or maintain a separate stripped data dict.

Proposed solution

preferences.anonymous: bool (default false). When true:

• Header renders label only (or a placeholder like "Candidate"), no name / photo / contact bar.
• PDF metadata author is set to a generic value.
• Same data dict, same compile command, single toggle.

Alternatives considered

• Tell users to compose a separate dict — error-prone (leaks if you forget a field) and loses the "single source of truth" of one CV file.