Add an optional estimated_release_at timestamptz column on posts. Editable only when status is Planned or Reviewing (or any non-terminal state - settable via project config). Supports both exact dates ("2026-08-12") and quarter-fuzz ("2026-Q3") via a small parser, stored as a date plus a precision enum (day, week, month, quarter).

Surfaces as a "Coming ~Aug" pill on cards, drives the Timeline view (separate post), and quietly clears itself when the post moves to Shipped (replaced by the actual ship date from status_history). Visible on the public roadmap when project is_public.