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/lint.sh

@@ -0,0 +1,131 @@
+#!/usr/bin/env bash
+# Unified linting script for all project code
+# Can be run manually or via git hooks
+
+set -e
+
+GREEN='\033[0;32m'
+RED='\033[0;31m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+NC='\033[0m'
+
+FAILED=0
+
+# Detect if we're in nix shell
+if ! command -v ruff &> /dev/null && command -v nix &> /dev/null; then
+    echo "🔄 Entering nix development environment..."
+    exec nix develop -c bash "$0" "$@"
+fi
+
+echo "========================================="
+echo "🔍 Reference Board Viewer - Code Linting"
+echo "========================================="
+echo ""
+
+# Backend Python linting
+echo -e "${BLUE}📦 Backend (Python)${NC}"
+echo "-----------------------------------"
+
+if [ -d "backend" ]; then
+    cd backend
+    
+    # Ruff check
+    echo -n "  Ruff check... "
+    if ruff check app/ 2>&1 | grep -q "All checks passed!"; then
+        echo -e "${GREEN}✓${NC}"
+    else
+        echo -e "${RED}✗${NC}"
+        echo ""
+        ruff check app/
+        FAILED=1
+    fi
+    
+    # Ruff format check
+    echo -n "  Ruff format... "
+    if ruff format --check app/ > /dev/null 2>&1; then
+        echo -e "${GREEN}✓${NC}"
+    else
+        echo -e "${RED}✗${NC}"
+        echo ""
+        echo "Run: cd backend && ruff format app/"
+        FAILED=1
+    fi
+    
+    cd ..
+else
+    echo -e "${YELLOW}  ⚠ Backend directory not found, skipping${NC}"
+fi
+
+echo ""
+
+# Frontend linting
+echo -e "${BLUE}🎨 Frontend (TypeScript/Svelte)${NC}"
+echo "-----------------------------------"
+
+if [ -d "frontend" ] && [ -f "frontend/package.json" ]; then
+    cd frontend
+    
+    # Check if node_modules exists
+    if [ ! -d "node_modules" ]; then
+        echo -e "${YELLOW}  ⚠ node_modules not found, run 'npm install' first${NC}"
+        cd ..
+    else
+        # ESLint
+        echo -n "  ESLint... "
+        if npm run lint > /dev/null 2>&1; then
+            echo -e "${GREEN}✓${NC}"
+        else
+            echo -e "${RED}✗${NC}"
+            echo ""
+            npm run lint
+            FAILED=1
+        fi
+        
+        # Prettier check
+        if [ -f ".prettierrc" ]; then
+            echo -n "  Prettier... "
+            if npx prettier --check src/ > /dev/null 2>&1; then
+                echo -e "${GREEN}✓${NC}"
+            else
+                echo -e "${RED}✗${NC}"
+                echo ""
+                echo "Run: cd frontend && npx prettier --write src/"
+                FAILED=1
+            fi
+        fi
+        
+        # TypeScript check
+        echo -n "  TypeScript... "
+        if npm run check > /dev/null 2>&1; then
+            echo -e "${GREEN}✓${NC}"
+        else
+            echo -e "${RED}✗${NC}"
+            echo ""
+            npm run check
+            FAILED=1
+        fi
+        
+        cd ..
+    fi
+else
+    echo -e "${YELLOW}  ⚠ Frontend directory not found, skipping${NC}"
+fi
+
+echo ""
+echo "========================================="
+
+if [ $FAILED -eq 0 ]; then
+    echo -e "${GREEN}✅ All linting checks passed!${NC}"
+    echo "========================================="
+    exit 0
+else
+    echo -e "${RED}❌ Some linting checks failed${NC}"
+    echo "========================================="
+    echo ""
+    echo "To auto-fix issues:"
+    echo "  Backend:  cd backend && ruff check --fix app/ && ruff format app/"
+    echo "  Frontend: cd frontend && npx prettier --write src/"
+    exit 1
+fi
+