feat(08-03): FavoriteLink schema + FavoritesModule (CRUD + SSRF icon discovery)

- Add FavoriteLink Prisma model (userId/tenantId/widgetId scope, iconUrl nullable, position)
- IconDiscoveryService: port SSRF-protected icon discovery with redirect: 'manual',
  private IP / blocked-hostname checks, 4000ms timeout, 200k HTML cap (T-08-05)
- FavoritesService: list/create/update/remove all scoped by userId (T-08-06 / Pitfall 3)
- FavoritesController: GET /favorites?widgetId, POST, PATCH :id, DELETE :id
- FavoritesModule registered in AppModule
- tsc --noEmit passes for @tessera/api

apps/api/src/favorites/dto/update-favorite.dto.ts

@@ -0,0 +1,27 @@
+import { IsInt, IsOptional, IsString, IsUrl } from 'class-validator';
+
+/**
+ * DTO for updating an existing FavoriteLink.
+ * All fields are optional — only provided fields are updated.
+ * iconUrl accepts null explicitly to clear a stored icon.
+ */
+export class UpdateFavoriteDto {
+  @IsOptional()
+  @IsString()
+  title?: string;
+
+  @IsOptional()
+  @IsUrl()
+  url?: string;
+
+  /**
+   * iconUrl can be a string (updated URL), null (clear icon), or absent (no change).
+   * No strict type validation so null passes through to Prisma.
+   */
+  @IsOptional()
+  iconUrl?: string | null;
+
+  @IsOptional()
+  @IsInt()
+  position?: number;
+}