feat: dashboard forecasts releases, tells what changed and weighs the load

The insights reading grows (GraphQL insights(since:), REST ?since=, MCP):
- planned releases with a likely (p50) and safe (p85) finish date from a
  Monte Carlo over the last six weeks of finished work, one after another,
  and a verdict against their target;
- with `since` (the viewer's last visit, kept in the browser): tickets
  created, finished and sent back from QA, and their mentions;
- each person's open points against what they closed per sprint lately;
- open tickets without estimate, area or assignee, or untouched for 90
  days, each count opening the list filtered (new noEstimate, noArea and
  updatedBefore filters).

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

libs/api/tracker/application/src/lib/queries/get-project-insights.query.ts

@@ -1,12 +1,17 @@
 import { Query } from '@nestjs/cqrs';
 import { ProjectInsightsReadModel } from '@task-stream/api/tracker/domain';
 
-/** The dashboard's reading of a project: sprint, risks, aging, bottlenecks. */
+/**
+ * The dashboard's reading of a project: sprint, risks, aging, bottlenecks,
+ * release forecasts, team load, backlog health and, with `since`, what
+ * changed after it.
+ */
 export class GetProjectInsightsQuery extends Query<ProjectInsightsReadModel> {
   constructor(
     /** Null: anonymous (public projects only). */
     public readonly viewerId: string | null,
     public readonly projectId: string,
+    public readonly since: Date | null = null,
   ) {
     super();
   }