chore: add pre-commit hook for protected branch validation

Adds a git hook that:
- Blocks commits to main/dev if validation fails
- Runs `make validate` for backend changes
- Runs `npm run validate` for frontend changes
- Skips validation for feature branches (can run manually)

To enable: git config core.hooksPath .githooks

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.githooks/pre-commit

@@ -0,0 +1,61 @@
+#!/bin/bash
+# Pre-commit hook to enforce validation before commits on protected branches
+# Install: git config core.hooksPath .githooks
+
+set -e
+
+# Get the current branch name
+BRANCH=$(git rev-parse --abbrev-ref HEAD)
+
+# Protected branches that require validation
+PROTECTED_BRANCHES="main dev"
+
+# Check if we're on a protected branch
+is_protected() {
+    for branch in $PROTECTED_BRANCHES; do
+        if [ "$BRANCH" = "$branch" ]; then
+            return 0
+        fi
+    done
+    return 1
+}
+
+if is_protected; then
+    echo "🔒 Committing to protected branch '$BRANCH' - running validation..."
+
+    # Check if we have backend changes
+    if git diff --cached --name-only | grep -q "^backend/"; then
+        echo "📦 Backend changes detected - running make validate..."
+        cd backend
+        if ! make validate; then
+            echo ""
+            echo "❌ Backend validation failed!"
+            echo "   Please fix the issues and try again."
+            echo "   Run 'cd backend && make validate' to see errors."
+            exit 1
+        fi
+        cd ..
+        echo "✅ Backend validation passed!"
+    fi
+
+    # Check if we have frontend changes
+    if git diff --cached --name-only | grep -q "^frontend/"; then
+        echo "🎨 Frontend changes detected - running npm run validate..."
+        cd frontend
+        if ! npm run validate 2>/dev/null; then
+            echo ""
+            echo "❌ Frontend validation failed!"
+            echo "   Please fix the issues and try again."
+            echo "   Run 'cd frontend && npm run validate' to see errors."
+            exit 1
+        fi
+        cd ..
+        echo "✅ Frontend validation passed!"
+    fi
+
+    echo "🎉 All validations passed! Proceeding with commit..."
+else
+    echo "📝 Committing to feature branch '$BRANCH' - skipping validation (run manually if needed)"
+fi
+
+exit 0