improvement(docker): speed up app image build with cache mounts and p… #15318

Job	Run time
Test and Build / Test and Build	48s
Detect Version	4s
Check Docs Changes	0s
Build Dev ECR	0s
Migrate Dev DB	0s
Build ARM64 (GHCR Only)	-1s
Build AMD64 (./docker/realtime.Dockerfile, ghcr.io/simstudioai/realtime, ECR_REALTIME)	35s
Build AMD64 (./docker/app.Dockerfile, ghcr.io/simstudioai/simstudio, ECR_APP)	3m 27s
Build AMD64 (./docker/db.Dockerfile, ghcr.io/simstudioai/migrations, ECR_MIGRATIONS)	37s
Create GHCR Manifests	0s
Create GitHub Release	0s
Process Docs	0s
	5m 30s

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