feat(hooks): run PHPUnit in pre-commit hook (#67)

Erweitert den Husky pre-commit-Hook um einen PHPUnit-Schritt.
Ausserdem wird scripts/safe-commit.sh aktualisiert, damit das
Safety-Net dieselbe Logik wie der Hook verwendet (kein doppelter Code).

Vorher: Hook rief nur 'npx lint-staged' auf.
Nachher: Hook ruft scripts/pre-commit-checks.sh auf, das
  - lint-staged ausfuehrt (unveraendert)
  - PHPUnit nur dann ausfuehrt, wenn PHP-relevante Dateien
    gestaged sind (Performance-Optimierung: Issue #67 Anforderung)
  - Bei Test-Fehler den Commit mit Exit-Code 1 abbricht

Closes #67

.husky/pre-commit

@@ -1 +1,3 @@
-npx lint-staged
+# Delegiert an scripts/pre-commit-checks.sh
+# (gleiche Logik wie safe-commit.sh-Safety-Net, nur einmalig)
+./scripts/pre-commit-checks.sh

scripts/safe-commit.sh

@@ -2,7 +2,7 @@
 # safe-commit.sh – Commit with pre-commit hooks guaranteed to run
 # Usage: ./scripts/safe-commit.sh "commit message"
 #
-# This script ensures lint checks always execute, even when committing
+# This script ensures lint + PHPUnit checks always execute, even when committing
 # from non-interactive contexts (CI, AI agents, etc.).
 
 set -euo pipefail
@@ -21,17 +21,9 @@ if [ -d ".husky" ]; then
   git config core.hooksPath .husky
 fi
 
-# Run lint-staged manually as a safety net (in case hook is skipped)
-if command -v npx &>/dev/null && [ -f "node_modules/.bin/lint-staged" ]; then
-  echo "🔍 Running pre-commit lint checks..."
-  npx lint-staged || {
-    echo ""
-    echo "❌ Lint checks failed. Commit aborted."
-    echo "   Fix the errors above and try again."
-    exit 1
-  }
-  echo "✅ All lint checks passed."
-fi
+# Run pre-commit checks manually as a safety net (in case hook is skipped)
+# Same logic as .husky/pre-commit, just in case the hook is bypassed.
+./scripts/pre-commit-checks.sh
 
 # Commit with hooks enabled (no --no-verify)
 git commit -m "$MSG"