Evaluate 1st-party templates for parallel deploy via uses field

Audit all Azure-maintained azd templates to identify which can leverage the `uses:` field in `azure.yaml` to enable parallel provisioning and deploy via the exegraph scheduler (#7776).

## Goal

Classify every 1st-party template into:

1. **Independent services** -- can deploy in parallel today with `uses:` expressing no deps (or future `execution.parallel: true` per #7995)
2. **Has dependencies** -- services with real ordering needs (e.g., API endpoint consumed by frontend deploy hook); add `uses:` to express the graph while unlocking parallelism for independent services
3. **Aspire-based** -- already parallel via build-gate, no action needed

## What to check per template

- Service-level hooks (`predeploy`/`postdeploy`) that read/write env vars or endpoints from other services
- Infrastructure outputs consumed by deploy steps
- Shared resources requiring sequential deploy access

## Deliverables

- [ ] Inventory of all 1st-party templates with classification
- [ ] PRs adding `uses:` to templates that benefit
- [ ] Validation that `azd deploy` produces correct results for representative templates

## Related

- #7776 -- exegraph execution engine
- #7995 -- explicit parallel deploy opt-in for non-Aspire templates