refactor: migrate backend to pnpm monorepo with Hono module architecture

- Replace Bun with pnpm 9 + Turborepo + tsx; apps/api renamed to apps/backend
- Split backend into http/, modules/, lib/ layers mirroring tai-specguard
- Add use-case + Result pattern, Problem Details RFC 7807, basePath /api/v1
- Mount Better Auth at /api/v1/auth, keep session-auth whitelist
- Split Prisma schema into prisma/models/*, generate into generated/
- Rework packages/shared into lib/ + schemas/ with pagination DTOs
- Implement health, groups, students, payments, waitlist modules
- Add vitest suite with prisma mocks (21 tests), biome lint
- Point web client to /api/v1/auth and /api/v1/groups/from-organization

apps/backend/src/logger.ts

@@ -0,0 +1,72 @@
+import { AsyncLocalStorage } from 'node:async_hooks';
+import pino from 'pino';
+import pinoPretty from 'pino-pretty';
+
+type LoggerEnvironment = {
+  nodeEnv?: string;
+};
+
+type RequestLogContext = {
+  requestId: string;
+};
+
+const requestLogContext = new AsyncLocalStorage<RequestLogContext>();
+
+const prettyOptions = {
+  colorize: true,
+  translateTime: 'SYS:standard',
+  ignore: 'pid,hostname',
+};
+
+const getLoggerEnvironment = (): LoggerEnvironment => ({
+  nodeEnv: process.env.NODE_ENV,
+});
+
+const isDevelopmentEnvironment = (environment: LoggerEnvironment) =>
+  environment.nodeEnv !== 'production';
+
+const isTestEnvironment = (environment: LoggerEnvironment) => environment.nodeEnv === 'test';
+
+export const runWithRequestLogContext = <T>(requestId: string, callback: () => T): T =>
+  requestLogContext.run({ requestId }, callback);
+
+const getRequestLogMetadata = () => {
+  const context = requestLogContext.getStore();
+
+  if (!context) {
+    return {};
+  }
+
+  return { requestId: context.requestId };
+};
+
+export const createLoggerOptions = (environment: LoggerEnvironment): pino.LoggerOptions => ({
+  enabled: !isTestEnvironment(environment),
+  level: isDevelopmentEnvironment(environment) ? 'debug' : 'info',
+  mixin: () => getRequestLogMetadata(),
+  formatters: {
+    level(label, number) {
+      return {
+        level: number,
+        severity: label.toUpperCase(),
+      };
+    },
+  },
+});
+
+export const createLogger = (
+  environment: LoggerEnvironment = getLoggerEnvironment(),
+) => {
+  const options = createLoggerOptions(environment);
+  if (isTestEnvironment(environment)) {
+    return pino({ ...options, level: 'silent' });
+  }
+
+  if (isDevelopmentEnvironment(environment)) {
+    return pino(options, pinoPretty(prettyOptions));
+  }
+
+  return pino(options);
+};
+
+export const logger = createLogger();