fix(SEC-API-21): Add DTO validation for semantic/hybrid search body

Replace inline type annotations with proper class-validator DTOs for the
semantic and hybrid search endpoints. Adds SemanticSearchBodyDto,
HybridSearchBodyDto (query: @IsString @MaxLength(500), status:
@IsOptional @IsEnum(EntryStatus)), and SemanticSearchQueryDto (page/limit
with @IsInt @Min/@Max validation). Includes 22 new tests covering DTO
validation edge cases and controller integration.

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

apps/api/src/knowledge/search.controller.ts

@@ -1,10 +1,16 @@
 import { Controller, Get, Post, Body, Query, UseGuards } from "@nestjs/common";
 import { SearchService, PaginatedSearchResults } from "./services/search.service";
-import { SearchQueryDto, TagSearchDto, RecentEntriesDto } from "./dto";
+import {
+  SearchQueryDto,
+  TagSearchDto,
+  RecentEntriesDto,
+  SemanticSearchBodyDto,
+  SemanticSearchQueryDto,
+  HybridSearchBodyDto,
+} from "./dto";
 import { AuthGuard } from "../auth/guards/auth.guard";
 import { WorkspaceGuard, PermissionGuard } from "../common/guards";
 import { Workspace, Permission, RequirePermission } from "../common/decorators";
-import { EntryStatus } from "@prisma/client";
 import type { PaginatedEntries, KnowledgeEntryWithTags } from "./entities/knowledge-entry.entity";
 
 /**
@@ -112,14 +118,13 @@ export class SearchController {
   @RequirePermission(Permission.WORKSPACE_ANY)
   async semanticSearch(
     @Workspace() workspaceId: string,
-    @Body() body: { query: string; status?: EntryStatus },
-    @Query("page") page?: number,
-    @Query("limit") limit?: number
+    @Body() body: SemanticSearchBodyDto,
+    @Query() query: SemanticSearchQueryDto
   ): Promise<PaginatedSearchResults> {
     return this.searchService.semanticSearch(body.query, workspaceId, {
       status: body.status,
-      page,
-      limit,
+      page: query.page,
+      limit: query.limit,
     });
   }
 
@@ -138,14 +143,13 @@ export class SearchController {
   @RequirePermission(Permission.WORKSPACE_ANY)
   async hybridSearch(
     @Workspace() workspaceId: string,
-    @Body() body: { query: string; status?: EntryStatus },
-    @Query("page") page?: number,
-    @Query("limit") limit?: number
+    @Body() body: HybridSearchBodyDto,
+    @Query() query: SemanticSearchQueryDto
   ): Promise<PaginatedSearchResults> {
     return this.searchService.hybridSearch(body.query, workspaceId, {
       status: body.status,
-      page,
-      limit,
+      page: query.page,
+      limit: query.limit,
     });
   }
 }