feat: add domains, ideas, layouts, widgets API modules

- Add DomainsModule with full CRUD, search, and activity logging
- Add IdeasModule with quick capture endpoint
- Add LayoutsModule for user dashboard layouts
- Add WidgetsModule for widget definitions (read-only)
- Update ActivityService with domain/idea logging methods
- Register all new modules in AppModule

apps/api/src/ideas/dto/create-idea.dto.ts

@@ -0,0 +1,56 @@
+import { IdeaStatus, TaskPriority } from "@prisma/client";
+import {
+  IsString,
+  IsOptional,
+  IsEnum,
+  IsArray,
+  IsUUID,
+  IsObject,
+  MinLength,
+  MaxLength,
+} from "class-validator";
+
+/**
+ * DTO for creating a new idea
+ */
+export class CreateIdeaDto {
+  @IsOptional()
+  @IsString({ message: "title must be a string" })
+  @MaxLength(500, { message: "title must not exceed 500 characters" })
+  title?: string;
+
+  @IsString({ message: "content must be a string" })
+  @MinLength(1, { message: "content must not be empty" })
+  @MaxLength(50000, { message: "content must not exceed 50000 characters" })
+  content!: string;
+
+  @IsOptional()
+  @IsUUID("4", { message: "domainId must be a valid UUID" })
+  domainId?: string;
+
+  @IsOptional()
+  @IsUUID("4", { message: "projectId must be a valid UUID" })
+  projectId?: string;
+
+  @IsOptional()
+  @IsEnum(IdeaStatus, { message: "status must be a valid IdeaStatus" })
+  status?: IdeaStatus;
+
+  @IsOptional()
+  @IsEnum(TaskPriority, { message: "priority must be a valid TaskPriority" })
+  priority?: TaskPriority;
+
+  @IsOptional()
+  @IsString({ message: "category must be a string" })
+  @MaxLength(100, { message: "category must not exceed 100 characters" })
+  category?: string;
+
+  @IsOptional()
+  @IsArray({ message: "tags must be an array" })
+  @IsString({ each: true, message: "each tag must be a string" })
+  tags?: string[];
+
+  @IsOptional()
+  @IsObject({ message: "metadata must be an object" })
+  metadata?: Record<string, unknown>;
+}