feat: add Azure monitoring dashboard project (APIM + Container Apps)

[tungbq]

Summary

New project: azure-monitoring-dashboard — a .NET and a Java sample app behind Azure API Management, running on Azure Container Apps, instrumented for distributed tracing via Azure Monitor, plus an Azure Monitor Workbook giving RED metrics (rate/errors/duration), an SLO tile, and a log-filtering panel for root-cause analysis.

• dotnet-orders-api (ASP.NET Core, externally exposed via APIM) calls java-inventory-api (Spring Boot, internal-only) to reserve stock — a real cross-service, cross-language call chain to trace end to end.
• Deliberately uses two different, both-valid instrumentation patterns: .NET via the Azure.Monitor.OpenTelemetry.AspNetCore SDK, Java via the auto-instrumenting Application Insights Java agent (-javaagent, zero code changes) — worth comparing.
• Dashboard tool: Azure Monitor Workbook, chosen over Managed Grafana after an explicit pros/cons pass — Workbooks win on cost (no extra resource) and fit the "easy log filtering for root cause" requirement more directly via native KQL log panels.
• ~15% simulated failure rate in dotnet-orders-api on purpose, so the error-rate/SLO panels have real non-zero data instead of a flat 100% success line.

What was verified locally (no Azure credentials in this environment)

• Both apps build as real Docker images and run together on a shared Docker network; a real order flows through the full dotnet-orders-api → java-inventory-api chain (demo_project.sh, also wired as CI at .github/workflows/verify-azure-monitoring-dashboard.yml).
• Terraform: fmt, validate, and a full terraform plan resolve the entire local dependency graph correctly (every resource, reference, and attribute name confirmed against the actual installed provider schema via terraform providers schema -json) — plan only stops at the expected Azure-auth boundary (az CLI not present here).
• The Workbook JSON is well-formed and its structure was checked against real Microsoft example Workbooks.

What was NOT verified (documented in the project README as an explicit boundary)

• No real terraform apply — no Azure credentials available, same as every other Azure project in this repo. Section "3-Deploy to Azure" in the project README is the real deploy walkthrough, meant to be run against a real subscription.
• No live screenshots of the deployed Workbook/dashboard.

Test plan

• ./demo_project.sh run end-to-end — builds both images, places a real order through the cross-service chain, validates Terraform, validates Workbook JSON. All green.
• terraform fmt -check -recursive / terraform validate / terraform plan (dummy vars, no real apply)
• Main README.md project table updated (row 22)
• Real terraform apply against an actual Azure subscription (left for whoever deploys this for real — see project README)

https://claude.ai/code/session_01DgVRQrXf1xhAHKYsV2xVAQ