feat(lab-03): complete Phase 4 - Compute & EC2 lab

Phase Plans (5 files):
- 04-RESEARCH.md: Domain research on Docker limits, healthchecks, EC2 parallels
- 04-VALIDATION.md: Success criteria and validation strategy
- 04-01-PLAN.md: Test infrastructure (RED phase)
- 04-02-PLAN.md: Diátxis documentation
- 04-03-PLAN.md: Infrastructure implementation (GREEN phase)

Test Scripts (6 files, 1300+ lines):
- 01-resource-limits-test.sh: Validate INF-03 compliance
- 02-healthcheck-test.sh: Validate healthcheck configuration
- 03-enforcement-test.sh: Verify resource limits with docker stats
- 04-verify-infrastructure.sh: Infrastructure verification
- 99-final-verification.sh: End-to-end student verification
- run-all-tests.sh: Test orchestration with fail-fast
- quick-test.sh: Fast validation (<30s)

Documentation (11 files, 2500+ lines):
Tutorials (3):
- 01-set-resource-limits.md: EC2 instance types, Docker limits syntax
- 02-implement-healthchecks.md: ELB health check parallels
- 03-dependencies-with-health.md: depends_on with service_healthy

How-to Guides (4):
- check-resource-usage.md: docker stats monitoring
- test-limits-enforcement.md: Stress testing CPU/memory
- custom-healthcheck.md: HTTP, TCP, database healthchecks
- instance-type-mapping.md: Docker limits → EC2 mapping

Reference (3):
- compose-resources-syntax.md: Complete deploy.resources reference
- healthcheck-syntax.md: All healthcheck parameters
- ec2-instance-mapping.md: Instance type mapping table

Explanation (1):
- compute-ec2-parallels.md: Container=EC2, Limits=Instance Type, Healthcheck=ELB

Infrastructure:
- docker-compose.yml: 5 services (web, app, worker, db, stress-test)
  All services: INF-03 compliant (cpus + memory limits)
  All services: healthcheck configured
  EC2 parallels: t2.nano, t2.micro, t2.small, t2.medium, m5.large
- Dockerfile: Alpine 3.19 + stress tools + non-root user

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

labs/lab-03-compute/how-to-guides/check-resource-usage.md

@@ -0,0 +1,94 @@
+# How-to: Verificare l'Utilizzo delle Risorse
+
+Come monitorare l'utilizzo CPU e memoria dei container Docker.
+
+## Utilizzo Base
+
+### Snapshot Singolo
+
+```bash
+docker stats --no-stream
+```
+
+Output:
+```
+CONTAINER   NAME        CPU %     MEM USAGE / LIMIT   MEM %     NET I/O     BLOCK I/O   PIDS
+12345       lab03-web   0.01%     2.5MiB / 1GiB      0.24%     1.2kB / 0B  0B / 0B     2
+```
+
+### Monitoraggio in Tempo Reale
+
+```bash
+docker stats
+```
+
+Premi `Ctrl+C` per uscire.
+
+### Container Specifico
+
+```bash
+docker stats lab03-web
+```
+
+## Formattazione Avanzata
+
+### Solo Container e CPU/Memoria
+
+```bash
+docker stats --format "table {{.Container}}\t{{.CPUPerc}}\t{{.MemUsage}}"
+```
+
+### Output senza header
+
+```bash
+docker stats --no-stream --format "{{.Container}}: {{.CPUPerc}}, {{.MemUsage}}"
+```
+
+### Output CSV
+
+```bash
+docker stats --no-stream --format "{{.Container}},{{.CPUPerc}},{{.MemUsage}}"
+```
+
+## Interpretare l'Output
+
+### CPU Percentage
+- `0.01%` - Container idle
+- `50%` - Container usa mezza CPU
+- `100%` - Container usa 1 CPU completa
+- `>100%` - Container usa più di 1 CPU (multi-core)
+
+### Memory Usage
+- `2.5MiB / 1GiB` - Usati 2.5 MB su 1 GB di limite
+- `512MiB / 512MiB` - Al limite (potrebbe causare OOM)
+- `980MiB / 1GiB` - Vicino al limite (watch!)
+
+### Memory Percentage
+- `<50%` - Sotto l'half del limite (OK)
+- `50-80%` - Nella norma (monitorare)
+- `>80%` - Vicino al limite (attenzione)
+- `>95%` - A rischio di OOM kill
+
+## Troubleshooting
+
+### Container usa 0% CPU
+Container potrebbe essere idle o bloccato. Verifica:
+```bash
+docker exec lab03-web ps aux
+```
+
+### Memory usage alto
+Identifica il processo che usa più memoria:
+```bash
+docker exec lab03-web ps aux --sort=-%mem | head -5
+```
+
+### Container OOM killed
+Cerca "OOM" nei log:
+```bash
+docker inspect lab03-web --format '{{.State.OOMKilled}}'
+```
+
+## Vedi Anche
+- How-to: Testare Limits Enforcement
+- Reference: Compose Resources Syntax