Backport public azuredeploy.json for template 10 (ADO 5347719) (#515)

Resolves a pre-existing private-vs-public divergence at
infrastructure/infrastructure-setup-bicep/10-private-network-basic/azuredeploy.json.

Public has been on blob b8716c1 (regenerated by an external/hand process
to add uniqueString-based foundryName default + the missing
Microsoft.CognitiveServices/accounts/projects dependency) since the
2026-06-08 recovery PR #767. Private
stayed on blob 840868a (unchanged since PR
microsoft-foundry/foundry-samples-pr#18 in 2026-01-28).

The divergence surfaced today during deployment validation of PR #513
(sync exclude filtering moved into filter-stream.py): the
seed-marks-from-public.sh tree-equivalence check refused to synthesize
marks. This morning's reseed (run 27253358355) passed only because the
validation gate happened to include this file in SYNC_BLOCKED_PATHS,
causing seed-marks' build_dynamic_pathspecs() to exclude it from
comparison.

This PR converges private onto public's exact blob (byte-identical), so
future seed-marks-from-public.sh runs pass without workarounds.

Out of scope (filed as follow-up):
- main.bicep is identical on both sides; public's azuredeploy.json was
  hand-regenerated without updating main.bicep, so the source-vs-
  generated inconsistency exists on public too. Properly regenerating
  main.bicep + azuredeploy.json together is a separate task.

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Author: 3 people