Speed up CI with NuGet cache + solution-wide build

- setup-dotnet@v5 with cache: true persists ~/.nuget/packages between
  runs, keyed on **/*.csproj. Cold restore (~90s) becomes a tar
  extract on cache hit.
- Replace five sequential dotnet restore + five sequential
  dotnet build invocations with one each against PlanViewer.sln.
  MSBuild builds the dependency graph in parallel internally, and
  we save four MSBuild startup cycles.
- Tests still build via the solution build, then run with --no-build.

PlanViewer.Ssms and PlanViewer.Ssms.Installer are intentionally not in
PlanViewer.sln, so they remain excluded from CI as before.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: erikdarlingdata

.github/workflows/ci.yml

@@ -17,25 +17,17 @@ jobs:
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 8.0.x
+          cache: true
+          cache-dependency-path: '**/*.csproj'
 
       - name: Install WASM workload
         run: dotnet workload install wasm-tools
 
-      - name: Restore dependencies
-        run: |
-          dotnet restore src/PlanViewer.Core/PlanViewer.Core.csproj
-          dotnet restore src/PlanViewer.App/PlanViewer.App.csproj
-          dotnet restore src/PlanViewer.Cli/PlanViewer.Cli.csproj
-          dotnet restore src/PlanViewer.Web/PlanViewer.Web.csproj
-          dotnet restore tests/PlanViewer.Core.Tests/PlanViewer.Core.Tests.csproj
-
-      - name: Build all projects
-        run: |
-          dotnet build src/PlanViewer.Core/PlanViewer.Core.csproj -c Release --no-restore
-          dotnet build src/PlanViewer.App/PlanViewer.App.csproj -c Release --no-restore
-          dotnet build src/PlanViewer.Cli/PlanViewer.Cli.csproj -c Release --no-restore
-          dotnet build src/PlanViewer.Web/PlanViewer.Web.csproj -c Release --no-restore
-          dotnet build tests/PlanViewer.Core.Tests/PlanViewer.Core.Tests.csproj -c Release --no-restore
+      - name: Restore solution
+        run: dotnet restore PlanViewer.sln
+
+      - name: Build solution
+        run: dotnet build PlanViewer.sln -c Release --no-restore
 
       - name: Run tests
         run: dotnet test tests/PlanViewer.Core.Tests/PlanViewer.Core.Tests.csproj -c Release --no-build --verbosity normal