test: add comprehensive unit tests for utils and security

- Add security.test.ts: 36 tests for webhook validation, rate limiting
- Add circuit-breaker.test.ts: 31 tests for state transitions
- Add retry.test.ts: 25 tests for exponential backoff
- Add api-helper.test.ts: 25 tests for API abstraction
- Add optimistic-lock.test.ts: 11 tests for concurrency control
- Add summary-service.test.ts: 29 tests for profile system

Total: 157 new test cases (222 passing overall)

- Fix setup.ts D1 schema initialization for Miniflare
- Update vitest.config.ts to exclude demo files

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

vitest.config.ts

@@ -6,6 +6,8 @@ export default defineConfig({
     globals: true,
     environment: 'node',
     setupFiles: ['./tests/setup.ts'],
+    include: ['tests/**/*.test.ts'],
+    exclude: ['**/node_modules/**', '**/src/**/__test__/**', '**/src/**/__demo__/**'],
     coverage: {
       provider: 'v8',
       reporter: ['text', 'json', 'html'],