feat(search): add @tower/search package with Meilisearch client and helpers

Implements Task 2 of Plan 4 (Archive & Search): provides createMeiliClient,
configureIndex, indexMessage, and deleteMessage for use by the worker and API.

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

packages/search/jest.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  rootDir: 'src',
+};