feat: a roadmap of epics over time

Tickets get a start date next to their due date, both editable on the
ticket page. The Hoja de ruta tab lays the epics out over the months as
bars filled with their progress, with sprints and releases as landmarks
and a line for today.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/domain/src/lib/models/models.ts

@@ -116,6 +116,9 @@ export interface IssueSummary {
   rank: string;
   /** Estimate; null when nobody estimated it. */
   storyPoints: number | null;
+  /** Planned start and end (`YYYY-MM-DD`), for the roadmap. */
+  startDate: string | null;
+  dueDate: string | null;
   commentCount: number;
   updatedAt: string;
   version: number;
@@ -143,7 +146,6 @@ export interface Issue extends IssueSummary {
   description: string | null;
   reporter: UserRef;
   figmaUrl: string | null;
-  dueDate: string | null;
   links: IssueLink[];
   attachments: Attachment[];
   /** People following the ticket. */