feat: presence on tickets

A ticket's page beats every 10 s (touchPresence / PUT
/issues/{issue}/presence, with whether I am editing) and gets back who
else is there, editing ones first. Entries live in Redis, one hash per
ticket, and fade after 30 s without a beat; leaving the page takes me out
at once. Only for people who can read the ticket; never in the event
store. The ticket shows «Bob está editando · Ana también lo está viendo»
above its title; editing means a ticket or comment form is open or a
comment is being written.

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

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

@@ -1188,6 +1188,16 @@ export class SetIssueParentDto {
   parent!: string | null;
 }
 
+export class PresenceBodyDto {
+  @ApiPropertyOptional({
+    default: false,
+    description: 'Editing the ticket or writing a comment',
+  })
+  @IsOptional()
+  @IsBoolean()
+  editing = false;
+}
+
 export class ChecklistItemBodyDto {
   @ApiProperty({ example: 'Actualizar el changelog', maxLength: 300 })
   @IsString()