feat(audit): Apply TreatWarningsAsErrors=true to 160+ production csproj files

Sprint: SPRINT_20251229_049_BE_csproj_audit_maint_tests
Tasks: AUDIT-0001 through AUDIT-0147 APPLY tasks (approved decisions 1-9)

Changes:
- Set TreatWarningsAsErrors=true for all production .NET projects
- Fixed nullable warnings in Scanner.EntryTrace, Scanner.Evidence,
  Scheduler.Worker, Concelier connectors, and other modules
- Injected TimeProvider/IGuidProvider for deterministic time/ID generation
- Added path traversal validation in AirGap.Bundle
- Fixed NULL handling in various cursor classes
- Third-party GostCryptography retains TreatWarningsAsErrors=false (preserves original)
- Test projects excluded per user decision (rejected decision 10)

Note: All 17 ACSC connector tests pass after snapshot fixture sync

src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Corpus.Alpine/ApkBuildSecfixesExtractor.cs

@@ -1,7 +1,7 @@
 // -----------------------------------------------------------------------------
 // ApkBuildSecfixesExtractor.cs
 // Sprint: SPRINT_20251226_012_BINIDX_backport_handling
-// Task: BACKPORT-17 — Implement APKBUILD secfixes extraction
+// Task: BACKPORT-17 - Implement APKBUILD secfixes extraction
 // -----------------------------------------------------------------------------
 
 using Microsoft.Extensions.Logging;