Fix Live Activity lock screen rendering and polish multi-account auth.

Flatten widget layouts and use system colors so banner and expanded regions render on vibrant lock screens; migrate auth sessions per account to prevent double sign-in; scope app lock PIN to accounts; default clock description to "Clock In"; add architecture docs and deferred form validation on auth screens.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/README.md

@@ -0,0 +1,12 @@
+# beenvoice-app documentation
+
+| Document | Description |
+|----------|-------------|
+| [ARCHITECTURE.md](./ARCHITECTURE.md) | Routing, contexts, auth/accounts, tRPC, app lock, Live Activity, theming |
+| [../README.md](../README.md) | Setup, run, troubleshooting |
+| [../AGENTS.md](../AGENTS.md) | Agent conventions |
+
+## Related
+
+- [beenvoice docs](../../beenvoice/docs/README.md) — server API and web app
+- [Workspace README](../../README.md) — full-stack layout