Add environment database support

[rtcoder]

Summary

• add zero-dependency .env loading during bootstrap
• add .env.example with database connection settings and ignore local .env files
• add native PDO database config, lazy database service, query result helpers, and transaction wrapper
• add a fluent table query builder with select, where, ordering, limits, insert, update, and delete
• add attribute-driven database models with PrimaryKey, Guarded, and Cast attributes
• support model find, create, save, delete, hydrated casts, explicit guarded updates, and public column properties
• update create:model stubs to extend the base Model and define table names
• document .env configuration, database usage, query builder usage, and model conventions
• cover env loading, DSN building, DB queries, query builder behavior, model casts, guarded fields, and model persistence with feature tests

Tests

• composer validate --no-check-publish
• composer dump-autoload
• find src application tests -name '*.php' -print0 | xargs -0 -n1 php -l
• composer test
• php shift.php route:list
• php shift.php health