feat: add unified linting scripts and git hooks for code quality enforcement

- Introduced `lint` and `lint-fix` applications in `flake.nix` for unified linting of backend (Python) and frontend (TypeScript/Svelte) code.
- Added `scripts/lint.sh` for manual linting execution.
- Created `scripts/install-hooks.sh` to set up git hooks for automatic linting before commits and optional tests before pushes.
- Updated `README.md` with instructions for using the new linting features and git hooks.

scripts/install-hooks.sh

@@ -0,0 +1,102 @@
+#!/usr/bin/env bash
+# Install git hooks for the project
+
+set -e
+
+HOOKS_DIR=".git/hooks"
+SCRIPTS_DIR="scripts"
+
+echo "Installing git hooks..."
+echo ""
+
+# Create hooks directory if it doesn't exist
+mkdir -p "$HOOKS_DIR"
+
+# Pre-commit hook
+cat > "$HOOKS_DIR/pre-commit" << 'EOF'
+#!/usr/bin/env bash
+# Git pre-commit hook - runs linting before commit
+
+echo "🔍 Running pre-commit linting..."
+echo ""
+
+# Try to use nix run if available, otherwise use script directly
+if command -v nix &> /dev/null && [ -f "flake.nix" ]; then
+    # Use nix run for consistent environment
+    if ! nix run .#lint; then
+        echo ""
+        echo "❌ Linting failed. Fix errors or use --no-verify to skip."
+        echo "   Auto-fix: nix run .#lint-fix"
+        exit 1
+    fi
+else
+    # Fallback to script
+    if ! ./scripts/lint.sh; then
+        echo ""
+        echo "❌ Linting failed. Fix errors or use --no-verify to skip."
+        echo "   Auto-fix: ./scripts/lint.sh --fix"
+        exit 1
+    fi
+fi
+
+echo ""
+echo "✅ Pre-commit checks passed!"
+EOF
+
+chmod +x "$HOOKS_DIR/pre-commit"
+echo "✓ Installed pre-commit hook"
+
+# Pre-push hook (optional - runs tests)
+cat > "$HOOKS_DIR/pre-push" << 'EOF'
+#!/usr/bin/env bash
+# Git pre-push hook - runs tests before push (optional)
+# Comment out or remove if you want to push without running tests
+
+echo "🧪 Running tests before push..."
+echo ""
+
+# Backend tests (if pytest is available)
+if [ -d "backend" ] && command -v pytest &> /dev/null; then
+    cd backend
+    if ! pytest -xvs --tb=short; then
+        echo ""
+        echo "❌ Backend tests failed. Fix tests or use --no-verify to skip."
+        exit 1
+    fi
+    cd ..
+fi
+
+# Frontend tests (if npm test is available)
+if [ -d "frontend/node_modules" ]; then
+    cd frontend
+    if ! npm test -- --run; then
+        echo ""
+        echo "❌ Frontend tests failed. Fix tests or use --no-verify to skip."
+        exit 1
+    fi
+    cd ..
+fi
+
+echo ""
+echo "✅ All tests passed!"
+EOF
+
+chmod +x "$HOOKS_DIR/pre-push"
+echo "✓ Installed pre-push hook (optional - runs tests)"
+
+echo ""
+echo "========================================="
+echo "✅ Git hooks installed successfully!"
+echo "========================================="
+echo ""
+echo "Hooks installed:"
+echo "  • pre-commit  - Runs linting before commit"
+echo "  • pre-push    - Runs tests before push (optional)"
+echo ""
+echo "To skip hooks when committing:"
+echo "  git commit --no-verify"
+echo ""
+echo "To uninstall:"
+echo "  rm .git/hooks/pre-commit .git/hooks/pre-push"
+echo ""
+