refactor: convert to bun workspaces monorepo

- Move web app into apps/web/
- Create packages/shared/ with shared types
- Create plugins/decky-vault/ scaffold
- Root package.json manages workspaces only

apps/web/drizzle/0002_square_slayback.sql

@@ -0,0 +1 @@
+ALTER TABLE "user" ADD COLUMN "last_login_method" text;