feat(05-02): add SearchProvider backend with model, CRUD, and defaults

- Prisma model SearchProvider with userId/tenantId scoping
- Three default providers (Google/Bing/DuckDuckGo) as constants, always returned without DB seed
- GET/POST/DELETE search-providers endpoints on DashboardController
- Ownership verification on delete (T-05-07), default providers cannot be deleted
- CreateSearchProviderDto with class-validator: urlTemplate must contain {query} (T-05-08)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/prisma/schema.prisma

@@ -134,3 +134,15 @@ model WidgetInstance {
   @@index([userId])
   @@index([tenantId])
 }
+
+model SearchProvider {
+  id          String   @id @default(uuid())
+  userId      String?
+  tenantId    String?
+  name        String
+  urlTemplate String
+  isDefault   Boolean  @default(false)
+  createdAt   DateTime @default(now())
+
+  @@index([userId])
+}

apps/api/src/dashboard/dashboard.controller.ts

@@ -12,6 +12,7 @@ import {
 } from '@nestjs/common';
 import { Request } from 'express';
 import { DashboardService } from './dashboard.service';
+import { CreateSearchProviderDto } from './dto/create-search-provider.dto';
 import { CreateWidgetDto } from './dto/create-widget.dto';
 import { SaveLayoutDto } from './dto/save-layout.dto';
 import { UpdateWidgetConfigDto } from './dto/update-widget-config.dto';
@@ -30,6 +31,9 @@ import { UpdateWidgetConfigDto } from './dto/update-widget-config.dto';
  * - POST /dashboard/widgets        — create a new widget instance
  * - PATCH /dashboard/widgets/:id/config — update widget config
  * - DELETE /dashboard/widgets/:id  — remove a widget instance
+ * - GET  /dashboard/search-providers     — list default + user's custom providers
+ * - POST /dashboard/search-providers     — create a custom search provider
+ * - DELETE /dashboard/search-providers/:id — remove a custom provider
  */
 @Controller('dashboard')
 export class DashboardController {
@@ -92,4 +96,30 @@ export class DashboardController {
     const { userId } = this.extractContext(req);
     return this.dashboardService.removeWidget(id, userId);
   }
+
+  // --- Search Providers (05-02, D-15) ---
+
+  @Get('search-providers')
+  async getSearchProviders(@Req() req: Request) {
+    const { userId } = this.extractContext(req);
+    return this.dashboardService.getSearchProviders(userId);
+  }
+
+  @Post('search-providers')
+  async addSearchProvider(
+    @Req() req: Request,
+    @Body() dto: CreateSearchProviderDto,
+  ) {
+    const { userId, tenantId } = this.extractContext(req);
+    return this.dashboardService.addSearchProvider(userId, tenantId, dto);
+  }
+
+  @Delete('search-providers/:id')
+  async removeSearchProvider(
+    @Param('id') id: string,
+    @Req() req: Request,
+  ) {
+    const { userId } = this.extractContext(req);
+    return this.dashboardService.removeSearchProvider(id, userId);
+  }
 }

apps/api/src/dashboard/dashboard.service.ts

@@ -4,10 +4,46 @@ import {
 } from '@nestjs/common';
 import { Prisma } from '@prisma/client';
 import { PrismaService } from '../prisma/prisma.service';
+import { CreateSearchProviderDto } from './dto/create-search-provider.dto';
 import { CreateWidgetDto } from './dto/create-widget.dto';
 import { SaveLayoutDto } from './dto/save-layout.dto';
 import { UpdateWidgetConfigDto } from './dto/update-widget-config.dto';
 
+/**
+ * Default search providers (D-15).
+ * Returned as part of getSearchProviders even when no DB rows exist.
+ * userId null = global defaults — cannot be deleted by users.
+ */
+const DEFAULT_SEARCH_PROVIDERS = [
+  {
+    id: 'google',
+    userId: null,
+    tenantId: null,
+    name: 'Google',
+    urlTemplate: 'https://www.google.com/search?q={query}',
+    isDefault: true,
+    createdAt: new Date('2024-01-01'),
+  },
+  {
+    id: 'bing',
+    userId: null,
+    tenantId: null,
+    name: 'Bing',
+    urlTemplate: 'https://www.bing.com/search?q={query}',
+    isDefault: true,
+    createdAt: new Date('2024-01-01'),
+  },
+  {
+    id: 'ddg',
+    userId: null,
+    tenantId: null,
+    name: 'DuckDuckGo',
+    urlTemplate: 'https://duckduckgo.com/?q={query}',
+    isDefault: true,
+    createdAt: new Date('2024-01-01'),
+  },
+];
+
 /**
  * Service managing per-user dashboard layouts and widget instances.
  *
@@ -126,4 +162,59 @@ export class DashboardService {
       where: { id },
     });
   }
+
+  // --- Search Providers (05-02, D-15) ---
+
+  /**
+   * Returns the three default providers merged with any user-custom providers.
+   * Defaults are always returned even with an empty DB (no seed migration needed).
+   */
+  async getSearchProviders(userId: string) {
+    const custom = await this.prisma.searchProvider.findMany({
+      where: { userId },
+      orderBy: { createdAt: 'asc' },
+    });
+
+    return [...DEFAULT_SEARCH_PROVIDERS, ...custom];
+  }
+
+  /**
+   * Creates a user-custom search provider.
+   */
+  async addSearchProvider(
+    userId: string,
+    tenantId: string,
+    dto: CreateSearchProviderDto,
+  ) {
+    return this.prisma.searchProvider.create({
+      data: {
+        userId,
+        tenantId,
+        name: dto.name,
+        urlTemplate: dto.urlTemplate,
+        isDefault: false,
+      },
+    });
+  }
+
+  /**
+   * Removes a user-custom search provider.
+   * Verifies ownership — default providers (userId null) cannot be deleted (T-05-07).
+   */
+  async removeSearchProvider(id: string, userId: string) {
+    // Default providers have hardcoded IDs that won't exist in DB
+    const provider = await this.prisma.searchProvider.findUnique({
+      where: { id },
+    });
+
+    if (!provider || provider.userId !== userId) {
+      throw new NotFoundException(
+        `Search provider with id '${id}' not found`,
+      );
+    }
+
+    return this.prisma.searchProvider.delete({
+      where: { id },
+    });
+  }
 }

apps/api/src/dashboard/dto/create-search-provider.dto.ts

@@ -0,0 +1,18 @@
+import { IsNotEmpty, IsString, Matches } from 'class-validator';
+
+/**
+ * DTO for creating a custom search provider (D-15).
+ * urlTemplate must contain {query} placeholder for the search term.
+ */
+export class CreateSearchProviderDto {
+  @IsString()
+  @IsNotEmpty()
+  name!: string;
+
+  @IsString()
+  @IsNotEmpty()
+  @Matches(/\{query\}/, {
+    message: 'urlTemplate must contain {query}',
+  })
+  urlTemplate!: string;
+}