Add comprehensive database setup and user management system

- Implement PostgreSQL database schema with users and bookmarks tables
- Add database connection pooling with retry logic and error handling
- Create migration system with automatic schema initialization
- Add database CLI tools for management (init, status, validate, etc.)
- Include comprehensive error handling and diagnostics
- Add development seed data and testing utilities
- Implement health monitoring and connection pool statistics
- Create detailed documentation and troubleshooting guide

Database features:
- Users table with authentication fields and email verification
- Bookmarks table with user association and metadata
- Proper indexes for performance optimization
- Automatic timestamp triggers
- Transaction support with rollback handling
- Connection pooling (20 max connections, 30s idle timeout)
- Graceful shutdown handling

CLI commands available:
- npm run db:init - Initialize database
- npm run db:status - Check database status
- npm run db:validate - Validate schema
- npm run db:test - Run database tests
- npm run db:diagnostics - Full diagnostics

backend/test-db-setup.js

@@ -0,0 +1,117 @@
+/**
+ * Test script to verify database setup is working correctly
+ * This script tests the database connection, schema creation, and basic operations
+ */
+
+require('dotenv').config();
+const dbConnection = require('./src/database/connection');
+const dbInitializer = require('./src/database/init');
+const dbUtils = require('./src/database/utils');
+
+async function testDatabaseSetup() {
+    console.log('🧪 Testing Database Setup...\n');
+    
+    let testsPassed = 0;
+    let testsTotal = 0;
+    
+    function test(name, condition) {
+        testsTotal++;
+        if (condition) {
+            console.log(`✅ ${name}`);
+            testsPassed++;
+        } else {
+            console.log(`❌ ${name}`);
+        }
+    }
+    
+    try {
+        // Test 1: Database Connection
+        console.log('1. Testing database connection...');
+        await dbConnection.connect();
+        test('Database connection established', dbConnection.isConnected);
+        
+        // Test 2: Health Check
+        console.log('\n2. Testing health check...');
+        const health = await dbConnection.healthCheck();
+        test('Health check returns healthy status', health.healthy);
+        test('Connection pool is configured', health.poolSize >= 0);
+        
+        // Test 3: Database Initialization
+        console.log('\n3. Testing database initialization...');
+        await dbInitializer.initialize();
+        const status = await dbInitializer.getStatus();
+        test('Database initialization completed', status.healthy);
+        test('Migrations table exists', status.migrations.total >= 0);
+        
+        // Test 4: Schema Validation
+        console.log('\n4. Testing schema validation...');
+        const validation = await dbUtils.validateSchema();
+        test('Schema validation passes', validation.valid);
+        test('Required tables exist', validation.errors.length === 0);
+        
+        // Test 5: Table Operations
+        console.log('\n5. Testing table operations...');
+        const usersExist = await dbUtils.tableExists('users');
+        const bookmarksExist = await dbUtils.tableExists('bookmarks');
+        test('Users table exists', usersExist);
+        test('Bookmarks table exists', bookmarksExist);
+        
+        // Test 6: Basic Query Operations
+        console.log('\n6. Testing query operations...');
+        const queryResult = await dbConnection.query('SELECT 1 as test');
+        test('Basic query execution works', queryResult.rows[0].test === 1);
+        
+        // Test 7: Transaction Support
+        console.log('\n7. Testing transaction support...');
+        let transactionWorked = false;
+        try {
+            await dbConnection.transaction(async (client) => {
+                await client.query('SELECT 1');
+                transactionWorked = true;
+            });
+        } catch (error) {
+            console.error('Transaction test failed:', error);
+        }
+        test('Transaction support works', transactionWorked);
+        
+        // Test 8: Connection Pool Stats
+        console.log('\n8. Testing connection pool...');
+        const stats = dbConnection.getStats();
+        test('Connection pool statistics available', stats.connected);
+        test('Pool configuration is correct', stats.config && stats.config.max > 0);
+        
+        // Summary
+        console.log('\n📊 Test Results:');
+        console.log(`✅ Passed: ${testsPassed}/${testsTotal}`);
+        console.log(`❌ Failed: ${testsTotal - testsPassed}/${testsTotal}`);
+        
+        if (testsPassed === testsTotal) {
+            console.log('\n🎉 All database tests passed! Setup is working correctly.');
+        } else {
+            console.log('\n⚠️  Some tests failed. Check the output above for details.');
+        }
+        
+        // Display diagnostics
+        console.log('\n🔍 Database Diagnostics:');
+        const diagnostics = await dbUtils.diagnostics();
+        console.log(JSON.stringify(diagnostics, null, 2));
+        
+    } catch (error) {
+        console.error('\n❌ Database test failed:', error.message);
+        
+        if (error.code === 'ECONNREFUSED') {
+            console.log('\n💡 PostgreSQL is not running. To fix this:');
+            console.log('1. Install PostgreSQL if not already installed');
+            console.log('2. Start PostgreSQL service');
+            console.log('3. Create database: createdb bookmark_manager');
+            console.log('4. Update .env file with correct credentials');
+        }
+        
+        process.exit(1);
+    } finally {
+        await dbConnection.close();
+    }
+}
+
+// Run the test
+testDatabaseSetup();