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/Scheduler/StellaOps.Scheduler.WebService/StellaOps.Scheduler.WebService.csproj

@@ -4,6 +4,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="StellaOps.Scheduler.WebService.Tests" />

src/Scheduler/StellaOps.Scheduler.Worker.Host/StellaOps.Scheduler.Worker.Host.csproj

@@ -3,6 +3,7 @@
     <OutputType>Exe</OutputType>
     <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
   <ItemGroup>

src/Scheduler/Tools/Scheduler.Backfill/Scheduler.Backfill.csproj

@@ -5,6 +5,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <LangVersion>preview</LangVersion>
     <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 

src/Scheduler/__Libraries/StellaOps.Scheduler.ImpactIndex/StellaOps.Scheduler.ImpactIndex.csproj

@@ -3,6 +3,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="../StellaOps.Scheduler.Models/StellaOps.Scheduler.Models.csproj" />

src/Scheduler/__Libraries/StellaOps.Scheduler.Models/StellaOps.Scheduler.Models.csproj

@@ -4,6 +4,6 @@
     <LangVersion>preview</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
 </Project>

src/Scheduler/__Libraries/StellaOps.Scheduler.Persistence/StellaOps.Scheduler.Persistence.csproj

@@ -6,7 +6,7 @@
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <LangVersion>preview</LangVersion>
-    <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <RootNamespace>StellaOps.Scheduler.Persistence</RootNamespace>
     <AssemblyName>StellaOps.Scheduler.Persistence</AssemblyName>
     <Description>Consolidated persistence layer for StellaOps Scheduler module (EF Core + Raw SQL)</Description>

src/Scheduler/__Libraries/StellaOps.Scheduler.Queue/StellaOps.Scheduler.Queue.csproj

@@ -3,6 +3,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="StackExchange.Redis" />

src/Scheduler/__Libraries/StellaOps.Scheduler.Worker/Execution/PartitionHealthMonitor.cs

@@ -23,13 +23,13 @@ public sealed class PartitionHealthMonitor
     // Gauges for partition metrics
     private static readonly ObservableGauge<int> FuturePartitions = Meter.CreateObservableGauge<int>(
         "stellaops.partitions.future_count",
-        () => _lastFuturePartitionCounts.Select(kv =>
+        () => (_lastFuturePartitionCounts ?? new()).Select(kv =>
             new Measurement<int>(kv.Value, new KeyValuePair<string, object?>("table", kv.Key))),
         description: "Number of future partitions available per table");
 
     private static readonly ObservableGauge<int> DaysUntilExhaustion = Meter.CreateObservableGauge<int>(
         "stellaops.partitions.days_until_exhaustion",
-        () => _lastDaysUntilExhaustion.Select(kv =>
+        () => (_lastDaysUntilExhaustion ?? new()).Select(kv =>
             new Measurement<int>(kv.Value, new KeyValuePair<string, object?>("table", kv.Key))),
         description: "Days until partition exhaustion per table");
 

src/Scheduler/__Libraries/StellaOps.Scheduler.Worker/StellaOps.Scheduler.Worker.csproj

@@ -4,6 +4,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="../StellaOps.Scheduler.ImpactIndex/StellaOps.Scheduler.ImpactIndex.csproj" />