Ship Novya PWA with backend for deployable production use.

Fix production TypeScript builds and add DEPLOY.md so the app can be hosted from this repo.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/shared/constants/errorCodes.ts

@@ -0,0 +1,14 @@
+export const ERROR_CODES = {
+  INTERNAL_ERROR: 'INTERNAL_ERROR',
+  VALIDATION_ERROR: 'VALIDATION_ERROR',
+  NOT_FOUND: 'NOT_FOUND',
+  UNAUTHORIZED: 'UNAUTHORIZED',
+  FORBIDDEN: 'FORBIDDEN',
+  CONFLICT: 'CONFLICT',
+  RATE_LIMIT_EXCEEDED: 'RATE_LIMIT_EXCEEDED',
+  SERVICE_UNAVAILABLE: 'SERVICE_UNAVAILABLE',
+  DATABASE_UNAVAILABLE: 'DATABASE_UNAVAILABLE',
+  INVALID_CREDENTIALS: 'INVALID_CREDENTIALS',
+} as const;
+
+export type ErrorCode = (typeof ERROR_CODES)[keyof typeof ERROR_CODES];