Recover interrupted PostgreSQL installation

[azurras]

Summary

• validate the actual EDB installation boundary: exact registered package, publisher, install root, service binding, and runtime version
• recover safely when PostgreSQL runtime files exist without a completed service registration
• preserve/restore the PostgreSQL 16 service across retry and validation failures

Production evidence

• EDB PostgreSQL 18.4-1 package is registered; winget verified its installer hash
• postgres.exe is unsigned, so the former Authenticode runtime assertion was invalid
• PostgreSQL 16 is restored Automatic/Running; website and MongoDB remain healthy
• cutover downtime has not started

Verification

• PostgreSQL operations Pester: 27/27
• complete production Pester: 766 passed, 28 expected skips, 0 failures
• :website:check :cbell-lib:check --no-daemon --max-workers=2: BUILD SUCCESSFUL in 5m38s
• V1-V27 migration diff: 0