Refactor user identification: Normalize user mapping and update messages table

[Copilot]

This PR refactors the user identification system to eliminate data redundancy and improve data integrity by normalizing the database schema as requested in the issue.

Changes Made

Database Schema Normalization

• Added users table with id (primary key), email (unique), name, and created_at columns
• Modified messages table to replace redundant user_email and user_name columns with a single user_id foreign key
• Generated migration file (0001_outgoing_venus.sql) to safely transform the existing schema

User Management Logic

• Enhanced authentication flow in auth.ts to create or find users in the database during login
• Session management now includes user ID for efficient database operations
• Graceful error handling for OAuth edge cases (missing email)

Message System Updates

• WebSocket message creation (ws.ts) now uses user_id instead of storing duplicate user data
• Message retrieval API (messages.ts) efficiently joins with users table to return user information
• Maintains API compatibility - existing frontend code continues to work unchanged

Data Integrity Improvements

• Eliminated redundant user data storage in messages table
• Established proper foreign key constraints between messages and users
• Unique email constraint prevents duplicate user records
• Referential integrity ensures message authors always exist

Before/After Comparison

Before:

-- Messages table with redundant user data
CREATE TABLE "messages" (
  "id" serial PRIMARY KEY,
  "content" text NOT NULL,
  "user_email" varchar(255) NOT NULL,  -- Redundant
  "user_name" varchar(255),            -- Redundant
  "created_at" timestamp DEFAULT now()
);

After:

-- Normalized schema with proper relationships
CREATE TABLE "users" (
  "id" serial PRIMARY KEY,
  "email" varchar(255) NOT NULL UNIQUE,
  "name" varchar(255),
  "created_at" timestamp DEFAULT now()
);

CREATE TABLE "messages" (
  "id" serial PRIMARY KEY,
  "content" text NOT NULL,
  "user_id" integer NOT NULL REFERENCES "users"("id"),
  "created_at" timestamp DEFAULT now()
);

Testing

• ✅ All existing tests updated and passing (20/20)
• ✅ Application builds successfully without errors
• ✅ No breaking changes to public APIs
• ✅ Backward compatibility maintained for existing functionality

This normalization improves data integrity, reduces storage redundancy, and makes user management more efficient while maintaining full application functionality.

Fixes #56.

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[mahata]

@copilot Fix CI in GitHub Actions.

[Copilot]

@copilot Fix CI in GitHub Actions.

Fixed CI issue - there was an invalid 'pnpm' suffix in the drizzle-orm dependency version in package.json which was causing installation failures. Updated package.json and lockfile. Commit: d7655b4