feat: implement sign-in and log-in authentication routes

[chhayaprdn]

• Added POST /api/auth/sign-in endpoint with Supabase Auth integration
• Added POST /api/auth/log-in endpoint with Supabase Auth integration
• Implemented Zod validation for email and password requirements
• Added password confirmation validation for sign-in
• Email validation with lowercase transformation
• Password requires 8+ characters, 1 uppercase, 1 special symbol
• Added environment variables for local Supabase connection
• All tests passing successfully

Purpose

This PR implements the authentication endpoints required for user registration and login as given in Issue #7. These routes allow new users to create accounts and existing users to authenticate, with proper validation and security measures in place.

Changes

• Created /api/auth/log-in route for user authentication
  • Validates email and password format
  • Integrates with Supabase Auth for authentication
  • Returns user info and access token on success
• Created /api/auth/sign-in route for user registration
  • Validates email format and converts to lowercase
  • Validates password requirements (8+ chars, 1 uppercase, 1 special symbol)
  • Validates password confirmation matches
  • Integrates with Supabase Auth for secure user creation
• Added Zod validation schemas for input validation
• Configured local environment variables for Supabase connection
• All endpoints tested successfully with curl commands

Issue(s)

Closes #7

Additional Comments

• Pre-existing build errors in types/database.ts and app/admin/page.tsx are unrelated to these changes
• Using local Supabase instance for development (credentials in .env.local)

Checklists

• I have thoroughly followed the practices as listed in the contributing guideline
• I have linted and formatted all of the code locally
• I have merged all the latest changes into my feature branch and fix any merge conflicts that came up
• I have thoroughly explained the changes made in the Purpose and Changes sections
• I have kept my commit history tidy by having succinct commit titles and file changes that accurately reflect my commits