feat: a sprint calendar

A Calendario tab lays the project's sprints out month by month as bands,
with the releases and the tickets due on each day. Owners and admins plan
a sprint by clicking the day it starts, and the whole plan downloads as an
iCalendar file. Tickets can be searched by due-date range.

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

libs/api/tracker/presenters/src/lib/http/dto/requests.dto.ts

@@ -509,6 +509,22 @@ export class IssueSearchQueryDto extends PageQueryDto {
   @IsBoolean()
   noSprint?: boolean;
 
+  @ApiPropertyOptional({
+    format: 'date',
+    description: 'Due on or after this day',
+  })
+  @IsOptional()
+  @Matches(/^\d{4}-\d{2}-\d{2}$/)
+  dueFrom?: string;
+
+  @ApiPropertyOptional({
+    format: 'date',
+    description: 'Due on or before this day',
+  })
+  @IsOptional()
+  @Matches(/^\d{4}-\d{2}-\d{2}$/)
+  dueTo?: string;
+
   @ApiPropertyOptional({
     enum: IssueSort,
     enumName: 'IssueSort',