feat: custom fields per project

Text, number, date or option-list fields defined in the project settings
(archived, never removed; their type is fixed once saved). Tickets hold
them, edited in the side panel, listed under the title and filtered by
option in the list view; also over GraphQL, REST (?field=ID:value) and MCP.

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

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

@@ -1,5 +1,6 @@
 import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
 import {
+  CustomFieldType,
   IssueLinkType,
   IssuePriority,
   NotificationKind,
@@ -78,6 +79,20 @@ export class AreaOptionDto {
   @ApiProperty() archived!: boolean;
 }
 
+export class CustomFieldDefinitionDto {
+  @ApiProperty({ example: 'BROWSER' }) id!: string;
+  @ApiProperty({ example: 'Navegador' }) name!: string;
+  @ApiProperty({
+    enum: CustomFieldType,
+    enumName: 'CustomFieldType',
+    description: 'DATE values are YYYY-MM-DD',
+  })
+  type!: CustomFieldType;
+  @ApiProperty({ type: [String], description: 'The choices of a SELECT field' })
+  options!: string[];
+  @ApiProperty() archived!: boolean;
+}
+
 export class ProjectSettingsDto {
   @ApiProperty({ type: [WorkflowStatusDto], description: 'In board order' })
   statuses!: WorkflowStatusDto[];
@@ -86,6 +101,8 @@ export class ProjectSettingsDto {
   @ApiProperty({ type: [IssueTypeOptionDto] })
   issueTypes!: IssueTypeOptionDto[];
   @ApiProperty({ type: [AreaOptionDto] }) areas!: AreaOptionDto[];
+  @ApiProperty({ type: [CustomFieldDefinitionDto] })
+  customFields!: CustomFieldDefinitionDto[];
 }
 
 export class ProjectDto {
@@ -426,6 +443,13 @@ export class IssueDto {
   startDate!: string | null;
   @ApiProperty({ type: String, nullable: true, format: 'date' })
   dueDate!: string | null;
+  @ApiProperty({
+    type: 'object',
+    additionalProperties: { type: 'string' },
+    example: { BROWSER: 'Safari' },
+    description: 'Custom field id → value (only those set)',
+  })
+  customFields!: Record<string, string>;
   @ApiProperty({ type: [IssueLinkDto] }) links!: IssueLinkDto[];
   @ApiProperty({ type: [AttachmentDto] }) attachments!: AttachmentDto[];
   @ApiProperty({ type: [UserRefDto], description: 'People following it' })