Feature/realtime poll server

[boytur]

This pull request includes significant updates to the backend of the application, focusing on adding new dependencies, updating the Prisma schema and migrations, seeding the database, and setting up the Express server with middleware.

Dependency Updates:

• backend/package.json: Added new dependencies such as bcrypt, express-validator, helmet, jsonwebtoken, morgan, and redis, along with their respective type definitions.

Prisma Schema and Migrations:

• backend/prisma/schema.prisma: Updated the schema to include new models (Event, Option, WhitelistUser, Guest, VoteRestriction) and modified existing models (User, Poll).
• backend/prisma/migrations/20250214050654_v_1/migration.sql: Removed old tables and constraints related to users, polls, poll_options, votes, poll_stats, and poll_option_stats.
• backend/prisma/migrations/20250216124341_init/migration.sql: Added new tables and constraints for User, Event, Poll, Option, WhitelistUser, Guest, VoteRestriction, and Vote.

Seeding the Database:

• backend/prisma/seeds/seed.ts: Created a seed script to populate the database with initial data, including an admin user, an event, polls, options, and guests.

Express Server Setup:

• backend/src/app.ts: Set up the Express server with middleware for CORS, security headers, logging, and JSON parsing. Added a basic route and a global error handler. Implemented graceful shutdown and connected to Prisma.

Prisma Client Initialization:

• backend/prisma/prisma.ts: Initialized and exported the Prisma client for database interactions.