Initial implementation of TriggerShell

A Python CLI (typer) that bootstraps Node/pnpm and launches a Next.js 16 web
app for running configured shell scripts: YAML config validated by a shared
Zod schema, dynamic per-script forms mapped to shadcn controls, argv-safe
execa execution with live WebSocket streaming, SQLite/Drizzle run history,
and optional argon2 session + API token auth.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/README.md

@@ -0,0 +1,16 @@
+# TriggerShell web app
+
+This is the Next.js app that TriggerShell's Python CLI (`triggershell dev` / `triggershell start`)
+launches — it's not meant to be run standalone with `next dev`/`next start` since it needs a
+custom server (`server.ts`) for the WebSocket endpoint.
+
+See the [repo root README](../README.md) for how to run TriggerShell end-to-end, and
+[`../docs/ARCHITECTURE.md`](../docs/ARCHITECTURE.md) for how this app is put together.
+
+```bash
+pnpm install
+pnpm dev          # tsx watch server.ts - reads TRIGGERSHELL_CONFIG_PATH from the environment
+pnpm lint
+pnpm typecheck
+pnpm db:studio    # browse the SQLite database
+```