feat: implement backend API for Pantree Phase 1 MVP

- Project setup: package.json, tsconfig.json, jest.config.js, .env.example
- Config: env.ts, constants.ts (ALLOWED_UNITS, bcrypt rounds, JWT, deletion windows)
- DB: Knex connection, knexfile, migrations 001-006 (users, password_reset_tokens,
  pantry_items, recipes+recipe_ingredients, shopping_lists+items, deleted_records)
- Seeds: 10 seeded recipes with full ingredient lists
- Middleware: JWT authMiddleware (validates token + user existence), errorHandler
- Utils: Pino logger, JWT sign helper, Zod validators for all request shapes
- Services: authService (signup/signin/google/pwd-reset/soft-delete/restore),
  pantryService (CRUD + case-insensitive duplicate guard),
  recipeService (browse+filter+scale), shoppingListService (CRUD+merge logic),
  syncService (delta sync + tombstone cleanup), emailService (SendGrid)
- Routes: /v1/auth, /v1/pantry, /v1/recipes, /v1/shopping-lists, /v1/sync
- App: Express factory (createApp), server entry point
- Jobs: node-cron daily hard-delete + tombstone cleanup
- Tests: validators, utils, auth, pantry, recipes, shopping lists, sync

jest.config.js

@@ -0,0 +1,24 @@
+/** @type {import('jest').Config} */
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  roots: ['<rootDir>/src'],
+  testMatch: ['**/*.test.ts'],
+  collectCoverageFrom: [
+    'src/**/*.ts',
+    '!src/**/*.test.ts',
+    '!src/db/knexfile.ts',
+    '!src/db/migrations/**',
+    '!src/db/seeds/**',
+    '!src/server.ts'
+  ],
+  coverageThreshold: {
+    global: {
+      branches: 70,
+      functions: 80,
+      lines: 80,
+      statements: 80
+    }
+  },
+  setupFiles: ['<rootDir>/src/test/setup.ts']
+};