feat(#166): Implement Stitcher module structure

Created the mosaic-stitcher module - the workflow orchestration layer
that wraps OpenClaw.

Responsibilities:
- Receive webhooks from @mosaic bot
- Apply Guard Rails (capability permissions)
- Apply Quality Rails (mandatory gates)
- Track all job steps and events
- Dispatch work to OpenClaw with constraints

Implementation:
- StitcherModule: Module definition with PrismaModule and BullMqModule
- StitcherService: Core orchestration logic
  - handleWebhook(): Process webhooks from @mosaic bot
  - dispatchJob(): Create RunnerJob and dispatch to BullMQ queue
  - applyGuardRails(): Check capability permissions for agent profiles
  - applyQualityRails(): Determine mandatory gates for job types
  - trackJobEvent(): Log events to database for audit trail
- StitcherController: HTTP endpoints
  - POST /stitcher/webhook: Webhook receiver
  - POST /stitcher/dispatch: Manual job dispatch
- DTOs and interfaces for type safety

TDD Process:
1. RED: Created failing tests (12 tests)
2. GREEN: Implemented minimal code to pass tests
3. REFACTOR: Fixed TypeScript strict mode issues

Quality Gates: ALL PASS
- Typecheck: PASS
- Lint: PASS
- Build: PASS
- Tests: PASS (12/12)

Token estimate: ~56,000 tokens

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

apps/api/src/app.module.ts

@@ -22,6 +22,7 @@ import { CronModule } from "./cron/cron.module";
 import { AgentTasksModule } from "./agent-tasks/agent-tasks.module";
 import { ValkeyModule } from "./valkey/valkey.module";
 import { BullMqModule } from "./bullmq/bullmq.module";
+import { StitcherModule } from "./stitcher/stitcher.module";
 import { TelemetryModule, TelemetryInterceptor } from "./telemetry";
 
 @Module({
@@ -31,6 +32,7 @@ import { TelemetryModule, TelemetryInterceptor } from "./telemetry";
     DatabaseModule,
     ValkeyModule,
     BullMqModule,
+    StitcherModule,
     AuthModule,
     ActivityModule,
     TasksModule,