FRE-608: Add Turso database setup with Drizzle ORM

- Create schema for users, projects, scripts, characters, scenes, revisions
- Implement DatabaseManager with connection pooling
- Implement EdgeDatabaseManager for multi-region replicas
- Implement DatabaseBackupManager with automated scheduling
- Generate initial migration with 9 tables
- Add seed script and documentation
- Configure Drizzle Kit for migration management
- Add NPM scripts for database operations

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.env.example

@@ -0,0 +1,13 @@
+# Turso Database Configuration
+TURSO_DATABASE_URL=libsql://<region>-<project>.turso.io
+TURSO_AUTH_TOKEN=<auth-token>
+
+# Backup Configuration (optional)
+BACKUP_INTERVAL_MS=86400000
+BACKUP_RETENTION_DAYS=30
+BACKUP_REGION=us-east
+
+# Clerk Authentication
+VITE_CLERK_PUBLISHABLE_KEY=pk_<your-publishable-key>
+VITE_CLERK_SIGN_IN_URL=/sign-in
+VITE_CLERK_SIGN_UP_URL=/sign-up