feat: add Features tab with linked Jira tickets and year-long backfill

- Add interactive Features tab to the dashboard with monthly charts,
  summary cards, and click-to-drilldown tables
- Backfill features-released.csv with 1 year of Jira data (1245 features)
- Epic IDs link directly to Jira (boomii.atlassian.net/browse/)
- Child tickets shown as teal pill badges with overflow indicator
- Drilldown modal filters by month, team, category, and visibility

Made-with: Cursor

Author: OhadPerryBoomi