Added Prisma migration to support user identification:
1. Session Table Enhancement
- Added user_id column (VARCHAR(36)) to session table
- Stores WordPress user ID for logged-in users
- Indexed for efficient lookups
2. User Mapping Table
- New table to track visitor_id to user_id relationships
- Maps anonymous visitors to authenticated users
- Tracks first_seen_at, last_seen_at, and session_count
- Unique constraint on (visitor_id, user_id) pair
3. Indexes
- idx_session_user_id - Fast user_id lookups
- idx_session_visitor_user - Composite index for visitor+user queries
- idx_user_mapping_visitor - Visitor ID lookups
- idx_user_mapping_user - User ID lookups
- idx_user_mapping_last_seen - Time-based queries
This migration enables unified user tracking across anonymous and authenticated sessions, supporting the WordPress plugin's user identification feature.