feat: tickets I follow, and more news for followers

"Que sigo" on the home page lists the open tickets I follow, whoever
works on them; `watching` filters my issues (REST, GraphQL, MCP) and a
project's search (none without a session).

Followers now also hear when a ticket's priority or due date changes,
and when it enters or leaves a sprint. Smaller edits (title, labels…)
still do not notify.

Docs (with the REPLIED row the replies change missed), Word and PDF
updated.

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

libs/api/tracker/presenters/src/lib/graphql/inputs.ts

@@ -508,6 +508,13 @@ export class IssueFilterInput {
   @IsOptional()
   @IsBoolean()
   noSprint?: boolean;
+  @Field({
+    nullable: true,
+    description: 'Only the tickets I follow (none when anonymous)',
+  })
+  @IsOptional()
+  @IsBoolean()
+  watching?: boolean;
   @Field({
     nullable: true,
     description: 'Due on or after this day (YYYY-MM-DD)',