Epic Lifecycle - auto-review gate and epics overview page

Child Tasks

• t-155.1 - Auto-transition epic to Review status when all children reach Done [Done]
• t-155.2 - Create /epics page listing all epics [Done]
• t-155.3 - Implement multi-color progress bar component (green=done, yellow=in-progress, blue=open) [Done]
• t-155.4 - Add status breakdown counts per epic on epics page [Done]
• t-155.5 - Link epics page from navbar Plans dropdown [Done]
• t-155.6 - Fix progress bar: show per-epic progress bar on /epics page, not aggregate bar on dashboard [Done]
• t-155.7 - Show aggregated execution metrics on epic detail page (total cost, total time from all subtasks) [Done]