feat(db): add PostgreSqlService with pg driver

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/unit/postgresql.test.ts

@@ -0,0 +1,70 @@
+/**
+ * Unit tests for PostgreSqlService
+ * These tests do not require a PostgreSQL instance
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest'
+import { PostgreSqlService } from '@main/services/database/postgresql'
+
+const mockConfig = {
+  host: 'localhost',
+  port: 5432,
+  user: 'test',
+  password: 'test',
+  database: 'testdb'
+}
+
+describe('PostgreSqlService Unit Tests', () => {
+  let service: PostgreSqlService
+
+  beforeEach(() => {
+    service = new PostgreSqlService(mockConfig)
+  })
+
+  describe('constructor', () => {
+    it('should create service with config', () => {
+      expect(service).toBeDefined()
+      expect(service.isConnected()).toBe(false)
+    })
+  })
+
+  describe('type', () => {
+    it('should return postgresql', () => {
+      expect(service.type).toBe('postgresql')
+    })
+  })
+
+  describe('isConnected', () => {
+    it('should return false when not connected', () => {
+      expect(service.isConnected()).toBe(false)
+    })
+  })
+
+  describe('query', () => {
+    it('should throw error when not connected', async () => {
+      await expect(service.query('SELECT 1')).rejects.toThrow('Not connected to PostgreSQL')
+    })
+  })
+
+  describe('transaction', () => {
+    it('should throw error when not connected', async () => {
+      await expect(service.transaction([{ sql: 'SELECT 1' }])).rejects.toThrow(
+        'Not connected to PostgreSQL'
+      )
+    })
+  })
+
+  describe('connect', () => {
+    it('should throw error with invalid host', async () => {
+      const invalidConfig = { ...mockConfig, host: 'invalid-host-that-does-not-exist' }
+      const invalidService = new PostgreSqlService(invalidConfig)
+      await expect(invalidService.connect()).rejects.toThrow('Failed to connect to PostgreSQL')
+    })
+  })
+
+  describe('disconnect', () => {
+    it('should resolve when not connected', async () => {
+      await expect(service.disconnect()).resolves.not.toThrow()
+    })
+  })
+})