Add `sm tinker` REPL (interactive C# shell with app DI loaded)

[antosubash]

Background

There is no interactive REPL with the app's DI container, EF context, services, and modules already wired up. Today, ad-hoc inspection means writing a throwaway endpoint or a one-off console project. Laravel Tinker drops you straight into a fully-bootstrapped session.

Motivation

• Quick one-off queries: db.Users.Count(), notifier.SendAsync(...), cache.SetAsync(...)
• Reproduce bug states fast
• Onboarding tool — devs poke at the framework live

Design sketch

New CLI command sm tinker:

• Uses dotnet-script (or Microsoft.CodeAnalysis.CSharp.Scripting directly)
• Boots the host (Host.CreateApplicationBuilder().Build()) so DI is identical to runtime
• Pre-imports common namespaces (SimpleModule.Core, all module Contracts, System.Linq)
• Pre-binds well-known services to globals: db, notifier, cache, events, currentUser (impersonate via flag)
• Multiline editor with history (Ctrl+R), tab-completion, color output
• --exec "<expr>" for non-interactive single-shot execution
• --user <id> to impersonate a user / tenant

Safety:

• Refuses to run against production unless --allow-prod and env var SM_TINKER_ALLOW_PROD=1

Acceptance criteria

• sm tinker command in cli/SimpleModule.Cli
• DI fully booted; common globals available
• History across sessions stored in ~/.simplemodule/tinker_history
• Tab-completion for type names + members
• --exec non-interactive mode
• Production guard
• Docs page with examples

References

• Laravel Tinker: https://laravel.com/docs/artisan#tinker
• dotnet-script: https://github.com/dotnet-script/dotnet-script