[Maintenance] - Retrospective End Date/Dropped WP Bugs

Description

The retrospective doesn't do its job. Changing the point of retro (date) doesn't do anything, and what currently fills out is random and not right, and is missing some work packages.

Acceptance Criteria

• changing the retro start/end date actually changes what shows in the retrospective view
• the retrospective correctly reflects every project's real work packages, with no missing or incorrect entries

Proposed Solution

• Add the missing end date picker to Restrospective.tsx. Currently, its headerRight only renders one DatePicker bound to startDate, even though RetroGanttFilters/buildRetroGanttParams (gantt.utils.tsx) already support endDate
• Fix the case bug at retrospective.services.ts:39 — change.detail.toLowerCase().includes('Added duration') compares a lowercased string against 'Added duration' (capital A), so that branch never matches; should be 'added duration'
• Work packages blocked by something outside the queried set get silently dropped; check getBlockingGanttTasks in gantt.utils.tsx

Mocks

No response

Start by reading Retrospective.tsx and the existing RetroGanttFilters/buildRetroGanttParams flow in gantt.utils.tsx to trace how the retrospective dates reach the view. Then inspect retrospective.services.ts:39 and getBlockingGanttTasks in gantt.utils.tsx; verify that changing both dates produces the expected project work packages, including items blocked outside the queried set.