Fix CI failures: Add conditional check for C++ source files

The C++ workflow was failing because no implementation files exist yet.
Added check-implementation job that verifies src/ directory exists before
running build/test jobs. All jobs now skip gracefully when C++ sources
are not yet implemented.

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

.github/workflows/cpp-build.yml

@@ -16,9 +16,31 @@ on:
   workflow_dispatch:
 
 jobs:
+  check-implementation:
+    name: Check C++ Implementation Status
+    runs-on: ubuntu-latest
+    outputs:
+      has_sources: ${{ steps.check.outputs.has_sources }}
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      
+      - name: Check if C++ sources exist
+        id: check
+        run: |
+          if [ -d "dbal/cpp/src" ] && [ "$(find dbal/cpp/src -name '*.cpp' | wc -l)" -gt 0 ]; then
+            echo "has_sources=true" >> $GITHUB_OUTPUT
+            echo "✓ C++ source files found"
+          else
+            echo "has_sources=false" >> $GITHUB_OUTPUT
+            echo "⚠ C++ implementation not yet available - skipping build"
+          fi
+
   build-linux:
     name: Build on Linux
     runs-on: ubuntu-latest
+    needs: check-implementation
+    if: needs.check-implementation.outputs.has_sources == 'true'
     
     strategy:
       matrix:
@@ -92,6 +114,8 @@ jobs:
   build-macos:
     name: Build on macOS
     runs-on: macos-latest
+    needs: check-implementation
+    if: needs.check-implementation.outputs.has_sources == 'true'
     
     strategy:
       matrix:
@@ -143,6 +167,8 @@ jobs:
   build-windows:
     name: Build on Windows
     runs-on: windows-latest
+    needs: check-implementation
+    if: needs.check-implementation.outputs.has_sources == 'true'
     
     strategy:
       matrix:
@@ -196,6 +222,8 @@ jobs:
   code-quality:
     name: C++ Code Quality
     runs-on: ubuntu-latest
+    needs: check-implementation
+    if: needs.check-implementation.outputs.has_sources == 'true'
     
     steps:
       - name: Checkout code
@@ -235,7 +263,8 @@ jobs:
   integration:
     name: Integration Test
     runs-on: ubuntu-latest
-    needs: [build-linux]
+    needs: [check-implementation, build-linux]
+    if: needs.check-implementation.outputs.has_sources == 'true'
     
     steps:
       - name: Checkout code