fix: Add generic delete method to ApiClient + CI speedups

- Add delete<T>() method to ApiClient for WorkersDashboard cleanup
- Add npm cache volume for faster npm ci
- Add TypeScript incremental builds with tsBuildInfoFile cache
- Should significantly speed up repeated CI runs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/src/index.ts

@@ -129,7 +129,6 @@ import { createStatesRouter } from './routes/states';
 import { createAnalyticsV2Router } from './routes/analytics-v2';
 import { createDiscoveryRoutes } from './discovery';
 import pipelineRoutes from './routes/pipeline';
-import { getPool } from './db/pool';
 
 // Consumer API routes (findadispo.com, findagram.co)
 import consumerAuthRoutes from './routes/consumer-auth';