feat: implement centralized structured logger utility (#24)

shared-utils/logger/.gitignore

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+node_modules/
+dist/
+coverage/

shared-utils/logger/README.md

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+# Structured Logger Utility (PoC)
+
+A standalone, decoupled Centralized Structured Logger for the TAP Buddy application.
+
+## Features
+- **Context Tagging**: Initialize with a context string (e.g. `AuthModule`) to easily trace logs.
+- **Severity Filtering**: Support for `DEBUG`, `INFO`, `WARN`, and `ERROR` levels with global and instance-level thresholds.
+- **Pluggable Transports**: By default, outputs beautifully formatted logs to the console. Can easily inject custom transports (e.g., Sentry, Crashlytics) for production environments via `Logger.setGlobalTransport()`.
+- **Zero Dependencies**: Core logic is implemented with pure TypeScript.
+
+## Quickstart
+
+```typescript
+import { Logger } from 'structured-logger';
+
+// Initialize with context
+const logger = new Logger('SyncEngine');
+
+logger.info('Starting sync process...', { userId: '123' });
+logger.error('Failed to connect to server');
+```
+
+## Running Tests
+This package is fully covered by a Jest test suite (100% coverage).
+```bash
+npm install
+npm test
+```

shared-utils/logger/jest.config.js

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+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  testMatch: ['**/tests/**/*.test.ts'],
+  collectCoverage: true,
+  coverageDirectory: 'coverage',
+  coverageThreshold: {
+    global: {
+      branches: 90,
+      functions: 90,
+      lines: 90,
+      statements: 90
+    }
+  }
+};