feat(#135): implement Quality Gate Configuration System

Add database-backed quality gate configuration for workspaces with
full CRUD operations and default gate seeding.

Schema:
- Add QualityGate model with workspace relation
- Support for custom commands and regex patterns
- Enable/disable and ordering support

Service:
- CRUD operations for quality gates
- findEnabled: Get ordered, enabled gates
- reorder: Bulk reorder with transaction
- seedDefaults: Seed 4 default gates
- toOrchestratorFormat: Convert to orchestrator interface

Endpoints:
- GET /workspaces/:id/quality-gates - List
- GET /workspaces/:id/quality-gates/:gateId - Get one
- POST /workspaces/:id/quality-gates - Create
- PATCH /workspaces/:id/quality-gates/:gateId - Update
- DELETE /workspaces/:id/quality-gates/:gateId - Delete
- POST /workspaces/:id/quality-gates/reorder
- POST /workspaces/:id/quality-gates/seed-defaults

Default gates: Build, Lint, Test, Coverage (85%)

Tests: 25 passing with 95.16% coverage

Fixes #135

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/quality-gate-config/dto/create-quality-gate.dto.ts

@@ -0,0 +1,37 @@
+import { IsString, IsOptional, IsBoolean, IsIn, IsInt, IsNotEmpty } from "class-validator";
+
+/**
+ * DTO for creating a new quality gate
+ */
+export class CreateQualityGateDto {
+  @IsString()
+  @IsNotEmpty()
+  name!: string;
+
+  @IsOptional()
+  @IsString()
+  description?: string;
+
+  @IsIn(["build", "lint", "test", "coverage", "custom"])
+  type!: string;
+
+  @IsOptional()
+  @IsString()
+  command?: string;
+
+  @IsOptional()
+  @IsString()
+  expectedOutput?: string;
+
+  @IsOptional()
+  @IsBoolean()
+  isRegex?: boolean;
+
+  @IsOptional()
+  @IsBoolean()
+  required?: boolean;
+
+  @IsOptional()
+  @IsInt()
+  order?: number;
+}

apps/api/src/quality-gate-config/dto/index.ts

@@ -0,0 +1,2 @@
+export * from "./create-quality-gate.dto";
+export * from "./update-quality-gate.dto";

apps/api/src/quality-gate-config/dto/update-quality-gate.dto.ts

@@ -0,0 +1,42 @@
+import { IsString, IsOptional, IsBoolean, IsIn, IsInt } from "class-validator";
+
+/**
+ * DTO for updating an existing quality gate
+ */
+export class UpdateQualityGateDto {
+  @IsOptional()
+  @IsString()
+  name?: string;
+
+  @IsOptional()
+  @IsString()
+  description?: string;
+
+  @IsOptional()
+  @IsIn(["build", "lint", "test", "coverage", "custom"])
+  type?: string;
+
+  @IsOptional()
+  @IsString()
+  command?: string;
+
+  @IsOptional()
+  @IsString()
+  expectedOutput?: string;
+
+  @IsOptional()
+  @IsBoolean()
+  isRegex?: boolean;
+
+  @IsOptional()
+  @IsBoolean()
+  required?: boolean;
+
+  @IsOptional()
+  @IsInt()
+  order?: number;
+
+  @IsOptional()
+  @IsBoolean()
+  isEnabled?: boolean;
+}