feat: add pre-commit hook setup script

- Add `scripts/setup-pre-commit.sh` to install a git pre-commit hook.
- The hook runs `npm run lint` and `npm run build:css` to enforce quality and build consistency.
- Update `CONTRIBUTING.md` to document the new hook setup under Development Setup.

scripts/setup-pre-commit.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+
+HOOK_FILE=".git/hooks/pre-commit"
+
+if [ ! -d ".git" ]; then
+  echo "Error: .git directory not found. This script must be run from the repository root."
+  exit 1
+fi
+
+echo "Setting up pre-commit hook at $HOOK_FILE..."
+
+cat > "$HOOK_FILE" << 'EOF'
+#!/bin/sh
+# pre-commit hook to run lint and build checks
+
+echo "Running pre-commit checks..."
+
+# Run lint
+echo "Running lint..."
+npm run lint
+if [ $? -ne 0 ]; then
+  echo "Lint failed. Please fix errors before committing."
+  exit 1
+fi
+
+# Run CSS build to ensure consistency
+echo "Running CSS build..."
+npm run build:css
+if [ $? -ne 0 ]; then
+  echo "CSS build failed. Please fix errors before committing."
+  exit 1
+fi
+
+echo "Pre-commit checks passed."
+EOF
+
+chmod +x "$HOOK_FILE"
+echo "Pre-commit hook installed successfully."